The frequency of drought events in Skierniewice, central Poland, over the last century

In the context of climate change, the frequency, intensity, and spatial distribution of drought events have become a critical area of research. Water scarcity can restrict plant development, reduce yields, and, under severe conditions, lead to total crop failure. This study investigates the occurrence and frequency of drought events in Skierniewice, central Poland, over the past 100 years (1923–2022), using historical meteorological data. Drought assessment was conducted using the standardised precipitation index (SPI), hydrothermal coefficient (HTC), thermal-precipitation index (Ped drought index) and climatic water balance (CWB). Based on the SPI classification, 34 dry years were identified during the study period. However, linear correlation analysis did not reveal statistically significant trends in SPI values over time, either on an annual basis or for individual months of the growing season. In contrast, correlation analyses of HTC and CWB values across the growing season showed a statistically significant negative linear trend for August, indicating increasing precipitation deficits during this month. Across all months, more periods are classified as dry according to HTC compared to SPI and Ped index, suggesting a greater sensitivity of this index to drought conditions. In the context of Skierniewice, the adopted HTC and CWB thresholds appear to accurately reflect drought conditions during spring and summer but may be overly restrictive for the later part of the growing season. Regardless of the index or classification criteria applied, droughts in Skierniewice have occurred relatively frequently, with severe events recorded both in the early and recent decades of the study period.