Prague has warm, occasionally showery summers and cold, often snowy winters with generally changeable conditions. A typical day in Prague from June to August sees the mercury range from about 12° to 22°C. Temperatures from December to February push below freezing. Wide variations are common, sometimes surpassing 35°C in summer and -20°C in winter. The summer's long, sunny, hot spells tend to be broken by sudden, heavy thunderstorms. In general, May and September enjoy the most pleasant weather.