Any season is good for a trip to Barcelona as it has a humid Mediterranean climate with average temperatures of around 15ºC. The summers are warm and the winters mild. Local fiestas and holidays offer a good excuse for a visit: World Book Day, which coincides with St George's Day (San Jordi) on April 23rd, is one of the most popular celebrations, along with La Merce, September 21st, which rounds the summer off with a packed festival programme. In recent years, rock and progressive music festivals have also become important in the city. Noteworthy among these are the Primavera Sound and Sonar festivals.