Summary:

Meteorological conditions have a considerable impact on water relations and the state of forest hydrogenic habitats. Variation in atmospheric precipita-tion and air temperatures are of particular relevance. The presented meteoro-logical parameters obtained between 1986 and 2008 from the meteorological station in Zielonka included: annual and halfyear precipitation sums; drought frequencies; number of days by quantity; mean annual and half-year air tempera-tures; number of days of different temperature categories; duration of the mete-orological growing season; beginning and completion of the meteorological growing season. The study results indicated the occurrence of changes in the values of the above-specified parameters. From 1987 to 2007 the mean precipitation value was 541 mm. In Zielonka nearly 5 droughts in a year and 2–3 during the summer half-years were noted. In recent years, a decrease in days with precipitation below 1 mm and above 20 mm was recorded. The mean annual air temperatures and mean temperatures of the winter and summer halfyears show a rising tendency. This is the result of changes in the number of days with extreme temperatures. In recent years, the number of days with the average temperature between -5.0 and 15.0°C has decreased while the number of days with temperature above +15.0°C has increased. The length of the meteorological growing season shows relative stability and equals 198 days. However earlier start and completion of the grow-ing season is noted.