Summary:

Meteorological conditions have a potential impact on forest economy. Var-iation in atmospheric precipitation and air temperatures are of particular relev-ance. The presented meteorological parameters obtained between 1987 (1986) and 2008 from the meteorological station in Zielonka included: annual, half-year and monthly precipitation sums; snow cover characteristic, drought frequencies; number of days by quantity; mean annual, half-year and monthly air temperatures; number of days of different temperature categories; duration of the meteorological growing season; beginning and completion of the meteorological growing season, period without slight frost. The study results indicated the occurrence of changes in the values of the above-specified parameters. From 1987 to 2008 the mean precipitation value was 531mm. In Zielonka nearly 5 droughts in
a year and 2-3 during the summer half-years were noted. In recent years, a de-crease in days with precipitation below 1mm was recorded. The mean annual air temperatures and mean temperatures of the winter and summer half-years 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 200 days. However earlier start and completion of the growing season is noted.