Posuchy atmosferyczne w Siedlcach w latach 1968-1997

The average monthly air temperatures and monthly sums of precipitation from the meteorological station in Siedlce from the years 1968-1997 were the basis of analyzis. Dry spells were determined with two methods: - Sielianinov’s hydrotermic index, - precipitation deficiency in relation to multiannual standards according to Kaczorowska. Average yearly precipitation in Siedlce was 461.1 mm in the analyzed years. The lowest monthly sums of precipitation in a growing season occured in April and October while the highest ones were observed in June and July. On the basis of data analyzis and evaluating the respective years, the years 1982 and 1991 have been assessed as dry (table 1) - following Kaczorowska’s criterion. The number of dry spell rnonths ranged from 0 to 5 in growing season (table 1 and 2). The highest number of exstreme droughts and strong dry spells was observed in October while light dry spells occured in July. The least cases of dry spells in a growing were encountered in June.