are always above 5 degrees Celsius with nights between and days between . Days are up to 16 hours long. Plzeň can be hot, especially during heat waves originating in the southern Mediterranean. The number of hot days above is steadily growing, with 5 months (late April – early September) of possible 30+ °C days. If hot weather does occur, it is often changes after a few weeks into cold and rainy weather with incoming Atlantic-based fronts. Nights can be unpleasantly cold even in summer, with high level of humidity. Winter frosts frequently occur from the second half of November to the end of March. February is the driest month with of precipitation, and July the wettest with . The only natural hazards are occasional fast changes of weather with negative consequences, e.g. floodings. Extreme values for years 2011 and 2012: An extremely cold day of 2011 had on average (23 February), and extremely hot day on average (24 August, . The year 2012 had the coldest day on 12 February with minimum plummeting to and maximum around with average . The hottest day of 2012 occurred on 21 August with daily maximum temperature and minimum staying on with all day average on . Absolute minimum and maximum for both years were (February 2012) and during August 2012. Number of rainy/snowy days for 2011: 78; number of days with frost: 76; number of days with minimal temperatures below : 12; number of days with average temperature below zero: 35; number of days with daily average temperature higher than : 188; number of days with daily average higher than : 32. Total amount of precipitation for year 2011: ; average year humidity value: 80.8%. Maximal temperature: ; minimal temperature . Average 2011 temperature: ; average speed of wind: , mainly from SSE. Number of days with frost was 96 during year 2012; 18 days had minima below and 165 days with an average temperature on or above . Number of days with maxima on or above was 42. Pilsner beer Plzeň is an important city in the history of beer, including the development of Pilsner. In 1375 Bohemian king Charles IV endowed the Dobrow Monastery near Plzeň with the beer right, and it is one of the oldest breweries to survive to modern times. Many breweries were located in the interconnected deep cellars of the city. The officials of Plzeň founded