San Diego enjoys a mild, temperate climate that has earned it worldwide appeal. Classified under the Köppen–Geiger system as either hot semi-arid (BSh/BSkn) or hot-summer Mediterranean (Csa), the city experiences warm, dry summers and mild, wet winters, with most rainfall occurring between December and March. Annual precipitation ranges from 9 to 13 inches (230–330 mm), and the city sees an average of 201 days per year above 70 °F (21 °C). Snow is extremely rare, recorded only a handful of times in over 150 years.

San Diego’s topography—including hills, mesas, canyons, and proximity to the bay—creates distinct microclimates. Coastal areas often remain cool due to the “marine layer,” especially during the May gray/June gloom period, while inland locations experience hotter summers and cooler winters. For example, downtown San Diego averages 50 °F (10 °C) in January and 78 °F (26 °C) in August, whereas inland El Cajon averages 42 °F (6 °C) in January and 88 °F (31 °C) in August.

The nearby Pacific Ocean also moderates temperatures, contributing to mild year-round conditions. Sea surface temperatures have risen nearly 3 °F (1.7 °C) since 1950, and the city’s hardiness zone is 11, reflecting the rare occurrence of frost. Higher elevations in the city receive slightly more rainfall, up to 11–15 inches (280–380 mm) annually, while coastal areas average 10.65 inches (271 mm). Rainfall is highly variable; the wettest years have exceeded 24 inches (610 mm), while drought years saw as little as 3.2 inches (80 mm).

This combination of sunny skies, mild temperatures, and diverse microclimates makes San Diego ideal for outdoor living, surfing, hiking, and year-round recreational activities, further enhancing the city’s reputation as one of the most livable coastal cities in the United States.