The present work describes the frequency of occurrence of dry spells and droughts periods in the vegetation season on the example of two localities distant from each other by about 40 km. In Bałcyny, which is situated in the Iława Lakeland, the investigation period included 36 years (1960-1995). In Pozorty-Tomaszkowo, which is situated in the Olsztyn Lakeland, the period of 1553-1995 (43-years) was investigated. High variability of the occurrence of dry spells and drought periods was found. Those periods were more frequent in Bałcyny (50%) than in Pozorty-Tomaszkowo (40%). In Bałcyny, the most threatening for vegetation dry spells appeared in July and August – when the probability of occurrence was 40%, whereas in Pozorty-Tomaszkowo the highest probability was in May – 53%, in June – 42%, and in August – 40%. The highest frequency of drought periods in Bałcyny was in August, September and October – 11%, while in Pozorty-Tomaszkowo in July and August – 14%.