Remarkable sequence of exceptionally wet and dry situations in Slovakia during the 3rd decade of the 21st Century

Since 2021, Slovakia has experienced several precipitation periods characterized by markedly divergent totals. Atmospheric precipitation exhibits substantial temporal and spatial variability, yet a novel pattern has emerged: prolonged dry spells (spanning several months or up to a year) alternating with extraordinary to extreme precipitation surpluses of much shorter duration.

This contribution presents longterm dry spells with sewere precipitation deficit folowed up by the heavy or extreme precipitation episodes overcoming historical maximum on records. The spatial distribution of precipitation from selected periods are visualized as gridded fields/layers.

At Bratislava-Letisko station, this phenomenon was recorded at the end of winter and the beginning of spring in the years 2021, 2022, and 2023. The 12-month period from September 2021 to August 2022 represented one phase of this disproportionately prolonged interval characterized by a precipitation deficit, especially in the lowland areas of Slovakia. In Nitra, only 463 mm of precipitation was recorded during the same period (September 2021–August 2022).

In contrast, an example of a pronounced precipitation surplus was observed in Nitra over a similarly long period from December 2022 to December 2023, when a total of 855 mm of precipitation was recorded. The alternation between precipitation-rich and precipitation-deficient periods has become particularly evident in recent years. For instance, following a precipitation-abundant June (231 mm recorded in Nitra) and September 2024 (132 mm recorded in Nitra), a subsequent 9-month period from October 2024 to June 2025 was characterized by a precipitation deficit, during which only 281 mm of precipitation was recorded in Nitra.

In September 2024, much of Central Europe experienced above-average precipitation. In mid-September, Storm Boris brought heavy rainfall, flooding, and significant damage to Central and Eastern Europe. The event is placed in a historical context by comparing its maximum, multi-day, and cumulative precipitation totals recorded between September 11 and September 16, 2024, with previous extreme precipitation occurrences. The results indicate that the highest-ever recorded 2-day (267.3 mm in Borinka) and 5-day (379.8 mm in Pernek) precipitation totals in Slovakia occurred during this event. More than 20% of stations with available data recorded new maximum 2-day or 5-day precipitation totals, with multi-day totals surpassing the 100-year and 200-year quantiles.