Buenos Aires has a humid subtropical climate ("Cfa" in the Koeppen climate classification). The average temperature is 17 °C. During the 20th century the temperature went up because of the urbanization. Rainfall is 1222.6 mm. per year. Summers are hot and humid. Winters are mild, the highest medium temperature is 13.7 °C during this season. Temperature rarely reaches 0 °C or below. Fog is frequent.