The Czech Republic has a temperate continental climate, with warm summers and cold, cloudy and snowy winters. The temperature difference between summer and winter is relatively high, due to the landlocked geographical position. Within the Czech Republic, temperatures vary greatly, depending on the elevation. In general, at higher altitudes, the temperatures decrease and precipitation increases. The wettest area in the Czech Republic is found around Bílý Potok in Jizera Mountains and the driest region is the Louny District to the northwest of Prague. The coldest months are January, February and December, which usually experience snow in the mountains and at times in the major cities and lowlands. During March, April and May, the temperature usually increases rapidly, especially during April, when the temperature and weather tends to vary widely during the day. Spring is also characterized by high water levels in the rivers, due to melting snow with occasional flooding. The warmest months of the year are July and August. On average, summer temperatures are between 20 and 30 °C higher than during winter. Summer is also characterized by rain and storms. Most rain falls during the summer. Sporadic rainfall is relatively constant throughout the year but concentrated heavy rainfall (days with more than 10 mm per day) are more frequent in the months of May to August.