Weather
Weather in Berlin is typical of Central Europe and regarded as moderate. The city has alternately sun and rain in all seasons. Summer is usually hot and the sky is often clear. Hottest months are June, July and August. Temperatures often rise in that season to 25 - 30 degrees Celsius. However, on cooler summer days temperatures are down to 15-20 degrees.
In winter temperatures fall. In December, January and February, they reach minus 1-2 degrees on average.
Tourist season reaches its peak in the summer. If you don't like the rush, time your vacation to spring and fall, although it's quite cool then (temperatures are normally 10-20 degrees). In any case, do not forget to bring an umbrella. Anyway, Berlin is a lovely city in all seasons.