Zmniejszenie częstości dni z burzą na przełomie czerwca i lipca w Poznaniu w latach 1961-1990

The study seeks to provide an explanation of why days with thunderstorms are less frequent at the close of June and the beginning of July in Poznań. Use was made of daily data from the Poznań- Ławica weather station of the Institute of meteorology and Water management (IMGW) from the years 1961-1990 on the occurrence of days with thunderstorms and diurnal means of air temperature and vapour pressure. The results of the study suggest that one of the immediate causes of the lower frequency of days with thunderstorms at the close of June and the beginning of July in Poznań in the period concerned is the increase in the number of days with mean diurnal temperature and vapour pressure lower than the lowest means of those meteorological elements for days with thunderstorms.