California (rightfully so) boasts of superb weather throughout the year, but conditions vary dramatically north to south.
The Central Valley areas are hot in summer, while chilly and foggy in winter. Most of southern California (Los Angeles, San Diego and the like) are protected from extreme temperatures because of the surrounding mountain ranges, so coastal cities are generally a bit cooler in summer.
Statewide, August and September are the warmest months, while January and February are the coolest.
San Francisco's weather is unpredictable with cloudy, cool and foggy conditions commonplace, and yet, the next day can be sunny with temperatures in the high 70's. Most agree that the city offers ideal weather conditions September through November.
The Cascade, Sierra Nevada, Yosemite and Lake Tahoe areas receive heavy winter snow. In the arid deserts of the southeast, and in Death Valley, extreme high temperatures are quite common.
The heaviest precipitation falls in the northern coastal areas.
For an interesting look at historical California precipitation (by regions) view this precipitation map.
Current Weather Conditions:
Seasonal Temperature Averages:
High Temperatures ( Fahrenheit/Celsius )
(Jan) 52/11 (Feb) 58/15 (Mar) 63/18 (Apr) 78/20
(May) 75/24 (Jun) 84/29 (Jul) 90/32 (Aug) 93/33
(Sep) 90/32 (Oct) 85/29 (Nov) 70/21 (Dec) 59/15
Low Temperatures ( Fahrenheit/Celsius )
(Jan) 39/3(Feb) 40/4 (Mar) 44/6 (Apr) 45/7
(May) 50/10 (Jun) 54/12 (Jul) 58/14 (Aug) 60/16
(Sep) 58/14 (Oct) 53/12 (Nov) 48/9 (Dec) 40/4