San Diego is blessed with a mild climate, low humidity, and good air quality. In fact, Pleasant Weather Rankings, published by Consumer Travel, ranked San Diego's weather number two in the world (behind Las Palmas, in the Canary Islands). It's worth keeping in mind, though, that San Diego County covers more than 4,500 square miles and rises in elevation from sea level to 6,500 feet. It can be a pleasant day on the coast but blisteringly hot on the inland mesas; or conversely, it can be a foggy day at the beach but gloriously sunny just minutes away downtown.
With its coastal setting, the city of San Diego maintains a moderate climate. Although the temperature can change 20° to 30° between day and evening, it rarely reaches a point of extreme heat or cold; daytime highs above 100°F (38°C) are unusual, and the mercury dropping below freezing can be counted in mere hours once or twice each year. San Diego receives very little precipitation (just 10 in. of rainfall in an average year); what rain does fall comes primarily between November and April, and by July, our hillsides start to look brown and parched. It's not unusual for the city to go without measurable precipitation for as long as 6 months in the summer and fall.
San Diego is busiest between Memorial Day and Labor Day. The kids are out of school and everyone wants to be by the seashore; if you visit in summer, expect fully booked beachfront hotels and crowded parking lots. The week of the July 4th holiday is a zoo at Mission Beach and Pacific Beach -- you'll either love it or hate it. But San Diego's popularity as a convention destination and its temperate year-round weather keep the tourism business steady the rest of the year, as well. The only slow season is from Thanksgiving to early February. Hotels are less full, and the beaches are peaceful and uncrowded; the big family attractions are still busy on weekends, though, with residents taking advantage of holiday breaks. A local secret: Although it's the coolest, rainiest season (relatively speaking, anyway), November through February are also the sunniest months of the year.
