Warsaw experiences an oceanic climate, denoted by Cfb by the Köppen climate classification. However, the city has clear humid continental influences , and the city is defined as such with old data, prior to the recent effect of climate change and the city’s urban heat island. Meanwhile, by the genetic climate classification of Wincenty Okołowicz, it has a temperate “fusion” climate, with both maritime and continental features.
The city has cold, sometimes snowy, cloudy winters, and warm, relatively sunny but frequently stormy summers. Spring and autumn can be unpredictable, highly prone to sudden weather changes; however, temperatures are usually mild and with low humidity, especially around May and September. The daily average temperature ranges between −1.8 °C (29 °F) in January and 19.2 °C (66.6 °F) in July and the mean year temperature is 8.5 °C (47.3 °F). Temperatures may reach 30 °C (86 °F) in the summer, although the effects of hot weather are usually offset by relatively low dew points and large diurnal temperature differences. Warsaw is Europe’s sixth driest major city (third in Eastern Europe), with yearly rainfall averaging 529 millimetres (20.8 in), the wettest month being July.