Poland is situated in a moderate climate zone. Warsaw receives a humid continental climate with warm summers, sunny autumns and cold, snowy winters. The climate in Warsaw is usually unpredictable so no matter the trend of the season, you should come prepared for colder climate.
Summer in Warsaw can be a grueling time if you happen to be not a fan of the heat. Summer in Warsaw, from June till September, is usually warm and humid or can vary from mild to exhaustingly hot. In most houses and some hotels, there is no air conditioning, which means the days and nights can be hot to the point of disturbing your sleep. You should bring light, summer clothes for the day, but in nights are definitely require some extra layers or jacket, which can sometimes get a little chilly.
While you will have to deal with a few wet days if visiting at this time, this is still the warmest, sunniest and generally most the pleasant time to experience Warsaw.
In October and November, considers temperatures drop from a mild 18°C in September to a cool 13°C in October and a cold 6°C in November. Night time temperatures drop accordingly and by November they near freezing. Snowfall often begins to fall in November and frosts are common from early in the month.
Once the leaves start falling in September and October, the temperature will generally remain mild, and autumn is one of the best times to visit the city. Warsaw is lovely in autumn as its many parks turn red and gold, so perhaps it is worth enduring a bit of dodgy grey weather.
The winter, on the other hand, has been known to be brutally cold and lasts from December till February. January and February are the driest months; about half of rain that does fall falls in the form of snow in lower areas, and exclusively as snow in the mountains.
From March till May, is mild and unpredictable. Spring conditions can vary greatly in Warsaw, from sunny sweater days already in March to snowfall in April; both have been known to happen, depending on the degree of the winter. But once spring comes, it does not take too long for the temperatures to warm up, at least when it’s not raining. By May, rainfall is almost at its highest levels. Unfortunately this means that Warsaw is a chance of flooding as the melted snow and heavy rain test the banks of the Vistula.