Assessment of historical heavy precipitation in Poland based on documentary evidence

Abstract. Anthropogenic climate change is intensifying the hydrological cycle and increasing extreme precipitation across much of Europe, yet understanding of pre-instrumental precipitation extremes in Central Europe remains limited by short instrumental records. This study presents the first comprehensive, documentary-evidence-based database of heavy and extreme precipitation events in Poland for the 12th–18th centuries. An assessment of a documentary-based database of heavy precipitation identified 477 such events. The extreme precipitation events were identified and classified into three types (long-lasting, heavy, or violent), based on reported impacts, duration, and affected regions. Results showed that the number of documented events increased over time, from a single event in the 12th century to 242 in the 18th century, with a peak of 182 events in the 1701–1750 sub-period. Silesia (37 %) and the Baltic Coast and Pomerania (28 %) were the most frequently affected regions, and summer accounted for the majority of all events. The duration of 273 events could be established, of which just over half lasted a single day. Notably, 316 impact assignments described damage never framed as a flood. These findings confirm that documentary sources capture fine-grained detail on the timing, duration, and consequences of past extreme-precipitation episodes, offering a valuable counterpart to multi-proxy reconstructions of longer-term hydroclimatic variability in Poland and Central Europe. This dataset offers a long-term baseline for evaluating present-day and projected changes in Central European precipitation extremes.