San Diego has a semi-arid climate and enjoys sunny and mild weather all year round, with only slight variation in temperature between the seasons. Occasional heat waves are caused by the hot Santa Ana winds blowing in from the desert, making it significantly hotter. That said, the temperatures in peak summer, between June and August, average between 62°F (17°C) and 76°F (24°C), while temperatures in winter, between December and February, range between 48°F (9°C) and 65°F (18°C). May and June are prone to fog. Rainfall is low, with most of it falling between November and April.