Białowieża experiences a temperate continental cool climate. The average annual air temperature is 6.8ºC. The average temperature in January is -4.7°C and in July 17.8°C with an average annual precipitation of 633 mm, most of which falls during the vegetation growth period. Winter is relatively long, and snow cover persists for over 92 days per year. The vegetation growth period is quite short (205 days), a month shorter than in western Poland.
The average temperature in May is 12.9°C, the mean daily maximum is 18.4°C and mean daily minimum 7.0°C. However, you should also be prepared for cold nights when the temperature can drop to 0°C. Rarely, during warm days, it can also rise up above 20-25°C. In May Białowieża receives 69 mm of rainfall. The average number of days with rainfall is 9.
Although May is only the beginning of the mosquito and tick season, better be prepared and take some repellent with you if you plan to spend much time in the forest.