Map from Google - Prague

The climate of Prague, the Czech capital, is moderately continental, with cold winters, in which the temperature is often below freezing (0 °C or 32 °F), and mild or pleasantly warm summers.
Here are the average temperatures.
Average temperatures - Prague
PragueJanFebMarAprMayJunJulAugSepOctNovDec
PragueJFMAMJJASOND
Min (°C)-5-4-137111212940-3
Max (°C)0381318212323191362
Min (°F)232530374552545448393227
Max (°F)323746556470737366554336

Precipitation is not abundant, given that it totals 530 millimetres (21 inches), but it is well distributed over the months, with a maximum between the second part of spring and summer, and a minimum in winter, when it usually occurs in the form of snow or sleet.
Here is the average precipitation.
Average precipitation - Prague
PragueJanFebMarAprMayJunJulAugSepOctNovDecYear
PragueJFMAMJJASONDY
Prec. (mm)252530407575657040303025525
Prec. (in)111.21.6332.62.81.61.21.2120.7
Days7667101099767790

Winter, from December to February, is cold: the average temperature is slightly below freezing. Due to stagnation of cold air in the lowest layers, there are many gray days, with snow typically light but quite frequent. On the other hand, cold air masses of Siberian origin can lead to intense frosts, in which the temperature can plunge below -20 °C (-4 °F). Here are some values recorded in particularly cold winters: February 1940: -29 °C (-20 °F); February 1956: -28 °C (-18 °F); January: 1985: -25 °C (-13 °F); January 1987: -24 °C (-11 °F); December 1996: -23 °C (-9 °F); February 2012: -22 °C (-8 °F).

Spring, from March to May, is a season characterized by an unstable weather, with the first warm days, but also the return of cold weather, with possible snow showers and frosts in March, but sometimes also in April. In early May it can still be cold, with lows near freezing. Typically, the temperature becomes mild in a more stable manner from the second half of May, the month in which also the first afternoon thunderstorms begin to erupt.

Summer, from June to August, is very mild or pleasantly warm: daytime temperatures hover around 21 °C (70 °F) in June and 23 °C (73 °F) in July and August. Atlantic fronts can pass in this season as well, bringing a bit of rain. On the contrary, in fine weather, thunderstorms can break out in the afternoon. In July and August, sometimes it can get hot, but all in all the days in which the temperature exceeds 30 °C (86 °F) are rare.

In Autumn, the first half of September is still pleasant, then gradually becomes gray and cloudy, with quite frequent rains. Already in October, the daytime temperature often remains below 15 °C (59 °F). The first snowfalls usually occur in November, which is in any case a cold month.

Prague

The amount of sunshine in Prague is quite good from May to August, when sunny days are frequent, and there are on average 8 hours of sunshine per day, while it is definitely low from November to February, when there are only 1/2 hours of sunshine per day.

When to go

The best time to visit Prague runs from mid-May to mid-September, being the warmest and sunniest of the year. Sometimes it can be hot in July and August, while in other circumstances nights can be cool, or even a little cold, even in these months, so it can be useful to bring a sweatshirt or sweater and a light jacket for the evening.