the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 16 Jul 2026
The June 2026 heatwave established a new benchmark for early-summer heat in German
Abstract. The June 2026 heatwave established a new benchmark for early-summer heat in Germany, producing the highest temperatures observed since instrumental records began and culminating in a new provisional national temperature record of 41.8 °C. Here, we quantify the extremeness of this event using high-resolution gridded observations, long-term station records extending back nearly two centuries, and ERA5 reanalysis, and investigate the relative contributions of atmospheric circulation and background climate warming. Across the 1951–2026 gridded record, the event ranks first in peak daily maximum temperature, cumulative heatwave intensity, and the number of days with daily maximum temperature exceeding 30 °C. Daily maximum temperature anomalies reached 12–16 °C locally, while regional peak temperatures exceeded the 1971–2000 climatology by up to 4.9 standard deviations and long-term station records by up to 3.7 standard deviations. At the national scale, heatwave duration and frequency have increased significantly since 1951, providing the long-term climatic context in which this event occurred. Flow-analogue analysis shows that the heatwave was generated by a persistent omega-type blocking anticyclone, but that comparable circulation patterns from the recent past would have produced 3–4 °C lower temperatures than those observed in 2026, indicating substantial thermodynamic amplification associated with background warming. Our results show that the June 2026 event represents a new class of intensity-dominated, record-shattering early-summer heatwaves in Germany, in which persistent atmospheric blocking acts upon a substantially warmer climate to produce unprecedented temperatures.
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Status: open (until 10 Sep 2026)
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RC1: 'Comment on egusphere-2026-4179', Milad Basirifard, 16 Jul 2026
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- The dynamic component is estimated from the mean T850 anomaly of the 25 closest Z500-pattern analogues, while the difference between that composite and the observed T850 anomaly is treated as the thermodynamic component. However, matching the pattern of Z500 anomalies does not guarantee that the circulation amplitude, pressure gradients, horizontal temperature advection, subsidence strength, or persistence are comparable. Indeed, the observed Z500 anomaly in Figure 11 appears substantially stronger than the analogue composite. Consequently, the reported 3 to 4 C residual may contain the effect of unmatched circulation intensity, antecedent soil moisture, advection, and other processes; not simply background warming. Could the authors repeat the analysis using analogues constrained by both Z500 pattern correlation and anomaly amplitude, or statistically adjust T850 for differences in Z500 amplitude? At minimum, the contribution associated with circulation mismatch should be quantified before the residual is described as evidence of thermodynamic amplification.
- The manuscript states that the 2001–2025 analogue composite is systematically warmer than the 1970–2000 composite on all five event days. However, Figure 12 appears to show the early-period composite warmer than the late-period composite on approximately 26–28 June, with only limited or reversed separation on the remaining days. This visual result does not support the stated systematic warming across all days. The authors should provide the exact daily values, uncertainty intervals, and statistical significance of the early minus late differences. They should also verify whether the plotted curves, legend, or textual interpretation are incorrect. This issue directly affects one of the paper’s central conclusions.
- The authors should define what constitutes a qualifying analogue, report similarity-distance distributions, account for unequal epoch lengths and repeated dates, and test whether the late-period excess differs from what would be expected by chance. Independent equal-sized analogue sets should also be selected within each epoch. In addition, Figure 13 visually labels the samples as n = 40 and n = 85, whereas its caption and main text report n = 38 and n = 87; this inconsistency must be corrected.
- Bootstrapping the 25 selected analogue days quantifies variability within that particular set, but it does not account for uncertainty arising from the choice of analogue number, European matching domain, distance metric, calendar window, epoch boundaries, or temporal dependence among analogue days. These choices are especially important because the authors acknowledge that the estimated dynamic–thermodynamic partition depends on them. A comprehensive sensitivity analysis should vary at least the number of analogues, matching domain, ±calendar window, similarity metric, and epoch boundary. A year block bootstrap would also be more appropriate than resampling individual days where analogues from adjacent dates or the same years may not be independent. Confidence intervals should be reported for the thermodynamic residual and early-versus-late difference, not only for the dynamic composite.
- The Methods define the standardized exceedance using the standard deviation of the daily temperature maximum series, whereas the Figure 5 caption states that the standard deviation is calculated from the regional annual-maximum series. These are fundamentally different distributions and could produce very different values, including the reported 4.9σ exceedance.
- Cumulative intensity is calculated as exceedance above the climatological mean, although heatwave days are selected using the 90th-percentile threshold. This formulation can mix event duration, seasonal climatology, and threshold exceedance in a way that may influence the rank-1 result. The authors should clarify the exact distributions used for P90 and σ, rename warming ratio as a standardized exceedance or z-score, and demonstrate robustness using alternative accepted heatwave metrics and thresholds, such as exceedance above P90, 95th-percentile definitions, and different minimum-duration criteria. The conclusion that the event was intensity-dominated should be shown to be insensitive to these methodological decisions.
- Trends in heatwave duration and frequency do not by themselves establish that an event of this magnitude must be expected to recur with increasing frequency and intensity. Such a statement requires an extreme-value or formal event-attribution analysis with estimated return periods and probability changes. The record claims also need more careful qualification because most heatwave metrics are restricted to May--June, whereas phrases such as the most intense heat event on record imply comparison with the complete warm season. In addition, the long-term station records require explicit information on homogenization, relocations, instrumentation changes, missing data, and urbanization effects. The station and HYRAS-DE analyses should not be presented as fully independent confirmation because HYRAS-DE itself is derived from station observations.
ReplyCitation: https://doi.org/10.5194/egusphere-2026-4179-RC1 -
RC2: 'Comment on egusphere-2026-4179', Anonymous Referee #2, 21 Jul 2026
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This manuscript provides a comprehensive statistical and synoptic analysis of the June 2026 heatwave. Daily maximum temperature during May and June of 2026 is compared to the historical record. Additionally, the overall trend of heatwaves across Germany is assessed. Lastly, the flow-analog approach is used to disentangle the dynamic and thermodynamic contribution of the June 2026 heat extreme. To this end the article employs observational records, the HYRAS_DE product and the ERA5 reanalysis data set.
The work provides a timely analysis of a meteorological extreme that is unprecedented for several common heatwave metrics. Analyzing this event can help the wider scientific community to better understand the dynamic and thermodynamic effects of climate change. However, I have significant reservations regarding the choice of the May-June reference period, the chapter 3.4, the quality of the flow-analogues, and the phrasing of certain conclusions. Nonetheless, I believe that the results of this study can relevant and valuable, if the following points are addressed:
General comments:
The choice of May-June as reference period seems arbitrary to me. Specifically, because the event peak occurred just at the end of the reference period. The Figure 5 b)-c) indicate that two separate heat wave events have occurred in succession (at least regionally) and that shifting the start of the reference period would significantly alter the extremeness of the event. Nonetheless, I do not think that completely rewriting the study into an event-based analysis is necessary. However, a more in-depth discussion of the rational when choosing the reference period is needed. I recognize that the conclusions are tailored to the May-June reference period. Nevertheless, a sensitivity analysis with varying start dates of the reference period can put the extremeness of the heatwave into context. This should be done, at least for the Germany-wide metrics, such as the standard exceedance and the rankings of Fig. 6.
On a related note, it should be made abundantly clear, when the May-June reference period is used and when the analysis uses data from the entire year. As I understand, in chapter 3.2 – 3.3 the May-June reference period is used and in chapter 3.4 the entire annual data is used. However, I am unsure whether this is even correct.
The first part of chapter 3.4 is lacking context, on how it fits into the wider field of research. Additionally, the spatial average trend values are missing for the German domain. I would expect a short overview of the results from similar studies, which analyzed the trend of heatwave frequency and intensity over Germany (i.e. Hundhausen et al., 2023). In this context the added value of this analysis should be presented. It would also be interesting to explore, how the single event of June 2026 has altered the long-term trend statistics. However, this is not an essential addition.
For the second part of chapter 3.4 the comparison aims to show, that past heatwaves were similarly extensive or similarly intense to the June 2026 event, but never both. However, this point is entirely undermined by the fact, that the selection criteria are not clearly presented. I have no context for either the 1953, or the 1976 event. Thus, this exemplary comparison does help with putting the June 2026 event into context.
Moreover, it is not clear to me that the selected analogues are a representative sample of the synoptic states from the 25th - 29th of June. I doubt the authors claim that the events have “[…] essentially the same circulation.” (l. 338). The quality assurance covers the Z500 residual (Fig. 11 c)), the Z500 pattern distance (Fig. S1) and the sampling uncertainty of the dynamic component of the analogue sample (Fig. 10). From Fig. S1 we can conclude, that the sample (chosen to represent the average state over the 25th – 29th) is significantly more representative of the June 2026 event than the average day on record. I am not able to interpret the absolute values of the Z500 distance. Figure 10 allows for the robust conclusion that the temperature difference between the June 2026 event and the sample is significant. However, neither of these Figures shows that the individual daily samples (N=125) are sufficiently similar of the atmospheric conditions of their respective counterparts. In fact, the Z500 residual between the average Z500 value over 25th -29th of June and their analogue (N=25) is very positive, with values above 75m (Fig. 11 c)). Perhaps, including a sensitivity analysis covering multiple sample sizes and multiple calendar window sizes would be helpful. Combining this with a more detailed analysis of the Z500 residuals could help explaining how much of the T850 anomaly is a thermodynamic effect.
Additionally, I see no temporal trend of the T850 anomaly between the 1970-2000 sample and the 2001-2025 sample. Figure 13 c) looks to be around zero on average for both the German and the large European domain. Figure 12 even shows lower values for the 2001-2025 analogues. In stark contrast the authors write: “The late-epoch analogue composite is systematically warmer than the early-epoch composite on all event days […]” (l. 353-354). Additionally, the authors write: “The pooled epoch composites (Figure 13) show that the analogue circulation patterns of the two epochs are nearly indistinguishable, while their temperature difference constitutes a coherent warming of the entire domain, except the British Isles.” (l. 360-362). In my opinion, they are both equally distinguishable.
Lastly, the claim of a “[…] new class of intensity-dominated, record-shattering early-summer heatwaves in Germany […]” (l. 24-25) is somewhat disconnected to the rest of the analysis. In line 410-411 the new class is defined as “short” and “record-shattering”. Neither “short”, nor “intensity-dominated”, nor “record-shattering” are defined in the text. In fact, I do not think the word “short” is particularly appropriate. The definition of “record-shattering” from (Fischer et al., 2021) states: “Events that break previous local records by large margins […]”. But the record-breaking margins that have been mentioned specifically (i.e. maximum absolute temperature) are in my opinion not large. However, some metric of the June 2026 heatwave may in fact be record-shattering.
Specific comment:
Fig. 1: The values for Figure 1 presumable relate to May-June 2026. In any case, the reference period should be mentioned.
Fig. 2: It may be useful to extent the upper bound of Fig. d) – f) to improve the visualization.
Fig. 4: In Fig. a) the “Baseline P90” label should be more visible. In Fig. b) I do not understand the purpose of the red dots showing the 2026 values of the individual regions. I believe the Germany-wide dot is sufficient. I assume “[...] the standard deviation of the regional annual-maximum series […]” is a typo and it meant to say "regional daily-temperature maximum series”.
Fig. 5: The Germany label could be highlighted in Fig. a). Additionally, I would like to see the graph of Fig. b) and c) for the entirety of Germany in the Supplement.
Fig. 8: The units of the color scheme is missing.
Fig. 11: Why is the event averaged over 5 days and the analogue composite the average of 25 different (probably independent) single-day events. Why is a 5-day-event-average compared to 25-day-average of unrelated single days? I would have expected this Figure using only a single day as an example, with the other 4 days in the Supplement. Afterwards, the 5 different residuals could be combined into the average residuals. A justification or citation of similar applications would be helpful.
L. 80-86: “Nevertheless, many heatwave studies remain focused either on synoptic dynamics or on statistical record-breaking, rather than on a combined observational diagnosis of event extremeness, long-term trend context, and circulation-based decomposition (Barriopedro et al., 2023; Fischer et al., 2021; Han et al., 2022; Luo et al., 2023; Vautard et al., 2019, 2023). Thus, a detailed case study of the June 2026 event can help bridge that gap by showing how unusual the event was in Germany, how it fits into longer-term changes, and how much of its intensity can be linked to circulation versus background warming.”
There any other studies analyzing both the statistical record-breaking and the synoptic dynamics of heatwaves. It would be appropriate to mention some of them here (i.e. Hotz et al., 2024).
L. 86-89: “Extreme temperatures occurring in late June are generally associated with larger societal impacts than comparable events later in the summer because ecosystems, agriculture, infrastructure, and the population are less acclimatized to prolonged heat.”
Some citation would be helpful.
L. 90-92: “Consequently, record-breaking heat occurring already in June represents an important indicator of the ongoing seasonal shift toward earlier occurrence of extreme temperatures.”
I believe “Consequently” is used incorrectly here, as the sentence does not relate causally to the previous point.
L. 133-134: “A heatwave event is defined as a period of at least five consecutive days during which TX exceeds this threshold.”
The rational or citations should be included to justify the decision of a 5 day exceedance. Especially, since other studies (Hundhausen et al., 2023) use 3 day exceedance.
L. 137-141: “Restricting the analysis to the available period ensures a consistent comparison between the 2026 event and the historical record. As the June heatwave accounts for the overwhelming majority of the early-summer temperature extremes in 2026, this restriction does not affect the interpretation of the event itself but should be considered when comparing seasonal heatwave metrics with previous years.”
The choice of reference period generally does affect the interpretation of the event. Relating to the first point in the general comments, I would prefer to see how exactly the choice of reference period affects the results.
L. 143-144: “[..] cumulative intensity, (i.e., defined as the sum over all heatwave days of the daily exceedance of TX above the calendar-day climatological mean).”
The choice of definition is lacking justification or citation. Alternative definitions (i.e. Russo et al, 2014) include such an in-depth discussion.
L. 146: “[..] standardized exceedance (“warming ratio”) [..]”
Perhaps it is simpler to use either one or the other, particularly, since “warming ratio” is rarely mentioned.
L. 168 - 169: “[..] restricting candidates to a ±15 day calendar window around the event date to preserve the seasonal cycle.”
A citation or additional explanation would be helpful, especially, since Jezequel et al. (2018) use ±30 days.
L. 216 – 217: “[…] was the highest value on record for that calendar day since 1970 […]”
Perhaps, the definition would be more precise if it said: “[..] are higher than any value on record for that calendar day since 1970 preceding the start of the event […]”. This avoids stippling the same grid points multiple days in a row, where the maximum is not on the last day.
L. 219-220: “[..] unprecedented lower-tropospheric temperature and mid-tropospheric geopotential-height anomalies […]”
I do not understand how extreme the geopotential-height anomalies are. A Supplement figure indicating the long-term quantile for the Z500 anomaly of the event would be helpful.
L. 219 – 222: “The spatial co-occurrence of unprecedented lower-tropospheric temperature and mid-tropospheric geopotential-height anomalies over the same region and days indicates that the event was extreme not only in terms of area-mean intensity, as shown in Section 3.2, but also at individual grid points in both T850 and Z500.”
Perhaps, breaking the sentence down into multiple sentences would make it easier to understand the content.
L. 257 – 258: “[…] the number of events (1, rank 6/76) […] ”
I am not sure if the number of events is a very relevant metric if a value of 1 places the June 2026 event at rank 4/76. The only conclusion I can draw from this is, that the June 2026 was probably rather long. In any case, it would be helpful to provide some guidance.
L. 401: “[…] comparatively short duration […]
Why “comparatively short”? Earlier, it was mentioned, that the event places 3/76 for number of heat days.
L. 425 – 426: “Similar large-scale atmospheric circulation states, now produce systematically higher temperatures than three decades ago […]”
This statement is not backed by Fig. 12 or 13, as previously mentioned. However, a citation could support this statement.
L. 429 – 431: “The quoted thermodynamic residuals should thus be regarded as combining background warming with the contribution of the event's extraordinary circulation amplitude and antecedent land- surface state.”
I agree. But I still do not feel like I have a qualitative understanding whether the 3–4 °C temperature anomaly is primarily driven by the background warming or if it is still the extraordinary circulation amplitude.
In conclusion, I recommend minor revisions.
References:
Fischer, E. M., Sippel, S., & Knutti, R. (2021). Increasing probability of record-shattering climate extremes. Nature Climate Change, 11(8), 689-695.
Hundhausen, M., Feldmann, H., Laube, N., & Pinto, J. G. (2023). Future heat extremes and impacts in a convection-permitting climate ensemble over Germany. Natural Hazards and Earth System Sciences, 23(8), 2873-2893.
Jézéquel, A., Yiou, P., & Radanovics, S. (2018). Role of circulation in European heatwaves using flow analogues. Climate dynamics, 50(3), 1145-1159.
Hotz, B., Papritz, L., & Röthlisberger, M. (2024). Understanding the vertical temperature structure of recent record-shattering heatwaves. Weather and Climate Dynamics, 5(1), 323-343.
Russo, S., Dosio, A., Graversen, R. G., Sillmann, J., Carrao, H., Dunbar, M. B., ... & Vogt, J. V. (2014). Magnitude of extreme heat waves in present climate and their projection in a warming world. Journal of Geophysical Research: Atmospheres, 119(22), 12-500.
Citation: https://doi.org/10.5194/egusphere-2026-4179-RC2 -
RC3: 'Comment on egusphere-2026-4179', Anonymous Referee #3, 23 Jul 2026
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I recommend major revision before the paper can be considered for publication.
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RC4: 'Comment on egusphere-2026-4179', Anonymous Referee #4, 03 Aug 2026
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This paper is well written and presents a timely analysis of a very recent extreme heatwave event in Europe, which deserves to be published. The study examines the June 2026 heatwave in terms of its dynamic and thermodynamic behaviour. I have only a few minor comments concerning spelling and consistency, which are listed below. Then I suggest to accept the paper for pubblication.
- line 51: change “arise” with “result”.
- line 70: delete “heatwave” for redundancy.
- line 77: change “towards” into “toward”.
- lines 90-92: This is a strong sentence. However, given that only an anomaly occurred in June 2026, it is not possible to assume a seasonal shift. Some reference concerning seasonal shifts for Germany should be included.
- line 101: change “to affect” into “affecting”.
- line 199: change “on the 29 June” into “on 29 June”.
- line 201: change “on the 27-28 June” into “on 27-28 June”.
- line 298: delete “to” before of TX.
- line 313: change “days counts” into “day counts”.
Citation: https://doi.org/10.5194/egusphere-2026-4179-RC4 -
RC5: 'Comment on egusphere-2026-4179', Wen Huo, 04 Aug 2026
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This study provides a timely and in-depth case study of the record-breaking late-June 2026 heatwave over Germany by utilizing high-resolution gridded datasets, centennial meteorological station records, ERA5 reanalysis data, and a flow-analogue decomposition framework. The overall structure of the manuscript is well-organized, offering valuable empirical insights into the spatial-temporal intensity and thermodynamic amplification characteristics of this extreme event. However, several critical methodological, logical, and phrasing issues in the text require revision. The overall comments for the manuscript are detailed below:
- The study sets out to explain the record-breaking surface daily maximum temperature (TX, Lines 97–100). However, the flow-analogue decomposition is performed entirely using 850 hPa temperature (T850, Lines 170–174), and the resulting ~3-4℃ residual is directly equated with the "background thermodynamic warming" of the surface heatwave (Lines 331–340, 421–446, 461–463). This creates a clear physical disconnect. T850 reflects conditions in the lower free troposphere, whereas surface TX is heavily modulated by local boundary-layer dynamics, soil moisture deficits, and radiative heating. A 3-4℃ warming at 850 hPa does not automatically translate into an equivalent 3-4℃warming at the surface. By conflating T850 with surface temperature, the manuscript overstates the physical meaning of the diagnosed residual. I recommend explicitly defining T850 as an indicator of lower-tropospheric thermal conditions and briefly discussing its limitations as a proxy for near-surface thermodynamic warming. If the authors insist on using T850 as the core metric for quantifying background warming, they must objectively justify the use of data at this pressure level as a proxy for near-surface thermodynamic warming.
- Lack of absolute quantitative assessment of analogue distance: Although the paper demonstrates that the algorithmically selected analogue days outperform random sampling, it fails to provide the absolute Euclidean distance between the historical analogues and the 2026 extreme circulation. Given the exceptional uniqueness of the ridge/blocking circulation during the June 2026 heatwave, if the absolute discrepancy of the best historical analogues remains large, the calculated positive residual may be contaminated by significant analogue mismatch errors. Consequently, it cannot be definitively confirmed that the residual stems purely from background thermodynamic warming.
- Lines 338–340: In Section 3.5, the statement that the analogue residual "should not be interpreted as a purely thermodynamic effect alone" implicitly attributes the residual to local land–atmosphere interactions. However, this claim is made without providing any supporting land-surface data (such as soil moisture or surface energy fluxes) in the Results section. Furthermore, it directly contradicts the authors' statement in Section 4 (Lines 454–455) that quantifying land-surface contributions is beyond the scope of this study. To maintain logical consistency and keep the Results section strictly empirical, please remove this qualifying phrase from Line 340 and restrict any speculative discussion on land-surface feedbacks to Section 4 as a tentative hypothesis.
- Line 465: The concluding assertion that such events "must be expected to recur with increasing frequency and intensity" is an overclaim that exceeds the empirical evidence presented in this paper. The manuscript relies strictly on historical trend analysis; it provides no climate model projections (e.g., CMIP6), counterfactual attribution simulations, Return Period calculations, or Extreme Value Theory (EVT) modeling to support explicit predictions about future event frequency or severity. Historical trends alone cannot be directly extrapolated to guarantee future recurrence behaviors. Please tone down this statement by framing future risks strictly within the context of observed historical trends rather than making definitive predictive assertions about future events.
- Line 465: There is a minor capitalization typo in the sentence "…that the HW event In June 2026…". The preposition "In" should be lowercased to "in" for grammatical consistency.
- Lines 473–478: Overinterpretation of Provisional Mortality Data. Quoting the specific figure of ~23,700 deaths from provisional Destatis data presents two main issues: (1) "All-cause mortality" includes deaths unrelated to heat, and no causal attribution was performed to isolate heat-driven excess deaths; (2) provisional statistics are subject to future revision. Please tone down this claim by explicitly stating that these figures are preliminary, unadjusted indicators, or clarify that a rigorous epidemiological attribution of excess mortality is beyond the scope of this study.
Citation: https://doi.org/10.5194/egusphere-2026-4179-RC5 -
RC6: 'Comment on egusphere-2026-4179', Anonymous Referee #6, 07 Aug 2026
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The manuscript presents a comprehensive analysis of the June 2026 heatwave in Germany. Overall, I find this a solid study. The manuscript addresses several aspects of this anomalous heat event, combining its spatial and temporal characterization, long-term context, and circulation-based analysis. Although the study is primarily diagnostic, its originality lies in the exceptional nature of the event itself, and its characterization provides useful information for improving our understanding of such extreme events and, as the authors mention, potentially contributing to their anticipation and preparedness. However, several methodological aspects require clarification before acceptance. My comments and suggestions are provided in the attached review.
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RC7: 'Comment on egusphere-2026-4179', Anonymous Referee #7, 08 Aug 2026
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General comments:
The manuscript is of high quality and well structured. However, the manuscript requires minor revision and language editing before it can be accepted for publication.
Specific comments and technical corrections:
Tables 1 and 2 are provided primarily for reference purposes and are not essential for the interpretation of the main results or discussion. Therefore, they are more appropriately placed in the Supplementary Material.
In the caption of Figure 1, “stated” should be replaced with “states”.
Line 124: Replace “X” with the multiplication sign “×”.
Line 212-215: The idea is too long; it should be split into two connected sentences.
Line 215-218: The idea is too long; it should be split into two connected sentences.
Line 226: ”for the 16 federal states and the Germany average” should be replaced with “for the 16 federal states and the national average for Germany”.
In the caption of Figure 4, ”for the 16 federal states and the Germany average” should be replaced with “for the 16 federal states and the national average for Germany”.
Line 253-258: The idea is too long; it should be split into two connected sentences.
In the caption of Figure 8, ”Long-term trends of heatwave characteristics over Germany, over the period 1951-2026” should be replaced with “Long-term trends of heatwave characteristics over Germany during 1951-2026”.
Line 309-312: The idea is too long; it should be split into two connected sentences.
Line 319: Remove “context”.
Line 320: Insert the letter “s” in “context”.
Line 322-327: The idea is too long; it should be split into two or three connected sentences.
Line 331-335: The idea is too long; it should be split into two connected sentences.
Line 347-352: The idea is too long; it should be split into two connected sentences.
Line 409: “Its compact duration…” should be replaced with “The short duration of the observed extreme event…”.
Line 413-416: The idea is too long; it should be split into two connected sentences.
Line 422: Insert the closing parenthesis symbol “)” after ridge.
Line 413-416: The idea is too long; it should be split into two connected sentences.
Line 456-459: The idea is too long; it should be split into two connected sentences.
Line 459: “It was produced…” should be replaced with “The observed extreme event was produced…”.
Line 464-467: The idea is too long; it should be split into two connected sentences.
Line 465: Use lowercase in “In June”.
Citation: https://doi.org/10.5194/egusphere-2026-4179-RC7 -
RC8: 'Comment on egusphere-2026-4179', Anonymous Referee #8, 08 Aug 2026
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Overview:
The manuscript presents a comprehensive and timely analysis of the late June 2026 heatwave event in Germany. It examines several aspects of this extreme heat event, characterising its severity and significance both spatially and temporally. The event is analysed using different metrics and utilising high-resolution gridded observations, long-term station records, and the ERA5 reanalysis. The analysis effectively enhances our understanding of dynamic and thermodynamic impacts of climate change on extreme weather events. The manuscript is generally well-written and easy to follow. It fits the scope of the journal and aims to address the unprecedented nature of the event. The figures, both in the main text and in the supplementary material, reflect most of what is written in the text. Overall, I recommend minor revisions.
Specific comments:
- Section 1: Perhaps it is worth adding a small paragraph on how common heatwaves are in Germany and when they mostly occur. This can provide some context on how different this event was compared to the climatological frequency of heatwaves in Germany.
- Section 2.4
- For the flow-analogue analysis, I was slightly confused by the use of the term “thermodynamical component” to refer to the “residual” and by what this terminology implies. My understanding is that the residual represents the difference between observed and analogue-composite anomalies, and that it points to a non-circulation component. However, considering that the authors state in the text (L. 340) that the analogue residual “should not be interpreted as a purely thermodynamic effect alone”, it could imply that other interactions might be contributing to the extremity of the event – a claim that is not directly supported by evidence in the manuscript. Perhaps this could be presented more explicitly as a hypothesis?
- Different epoch lengths, as well as different numbers of analogues within each epoch, are used in the analysis. Am I correct in understanding that there are twice as many analogues in the latest epoch (2001-2025) compared to the earliest epoch (1970-2000)? Please clarify this point and explain why this approach was preferred over using epochs of equal length with an equal number of analogues in each epoch.
Technical Corrections:
Font size in figures 1, 4, 5, 7, and 9 should be slightly bigger for better readability and to also match the font size on the rest of the figures.
Fig. 1:
- Typo “June 226” to “June 2026”;
- Are the label positions indicative of the location of stations? If not, perhaps it might be useful to include the locations of the stations on this figure.
Fig. 2: Maybe the anomalies can be shown with a different colormap? At first glance, I did not understand that the top and bottom rows show different quantities
Fig. 4: It is difficult to see the baseline
Fig. 5: On 5a, the label for Germany could be highlighted or be in bold
Fig. 7:
- On 7a, it is difficult to see the baseline, and it seems that the timeseries with the lowest values is not shown properly – perhaps change the lower limit of the y-axis
- On 7b, it is difficult to see the vertical line
- The caption says “the 2026 values are highlighted” but I am not sure I see it?
Fig. 8: The units are missing
Fig. 13: Caption and text (L. 364) say n=38 and n=87, but subplot titles say n=40 and n=85. Please clarify which is true.
L. 86 – 89: a citation would be useful
L. 90 – 92: The word “consequently” does not really follow the previous statements. Also, I am not sure whether one such event is sufficient to support the claim of “important indicator of the ongoing seasonal shift toward earlier occurrence of extreme temperatures”. The statement could be true if similar events were observed elsewhere across Europe.
L. 128: Change “Heatwaves (HW)” to “Heatwaves (HWs)”
L. 129: There is a typo for the “Hobday et al., 2016” citation
L. 131-132: “daily maximum temperature (TX)” has been previously defined. So, “TX” can be used instead
L. 133-134: Add a citation for the choice of 5 consecutive days
L. 229-230: I am not sure to which region the authors are referring from the statement “…by more than one standard deviation in all but one region…”. Is this shown on Figure 5a?
L. 266-267: “The 2026 values stand at or near the top of these ~180-year records at the majority of the stations.” Is this shown in a Table or Figure?
L. 270: Refer to Figure 7b specifically
L. 353-354: The text says “The late-epoch analogue composite is systematically warmer than the early-epoch composite on all event days…” but Figure 12 shows the opposite for 26-28 June. Please clarify this.
L. 361: It is probably best to change the words “are nearly indistinguishable” to “exhibit similar overall patterns with small differences in position and amplitude” and to state clearly that they refer to the black Z500 contours.
L. 449: Change “soil moisture” to “soil-moisture”
L. 465: Change “In June” to “in June”:
L. 464-465: I suggest altering this sentence slightly, from “…these results imply that the HW event In June 2026 must be expected to recur with increasing frequency and intensity…” to “these results suggest that HW events similar to the recent June 2026 event could become more frequent and intense…”
L. 470-472: I do agree that this event should alarm everyone and that we should start preparing for the possibility that such events might become more frequent. However, I think the sentence “…the occurrence of record-breaking temperatures already in June suggests that preparedness plans, public-health interventions, and early-warning systems should increasingly account for severe heat episodes occurring substantially earlier in the season” might need to be toned down a bit.
L. 473-478: Although it is mentioned that these are provisional data from Destatis, am I correct to understand that these data include deaths that are not necessarily attributed to heat stress caused by this event specifically? If so, please state it clearly.
Citation: https://doi.org/10.5194/egusphere-2026-4179-RC8
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