When to Go

Because they offer activities indoors and out, the top California cities rate as all-season destinations. Ditto for Southern California's coastal playgrounds. Dying to see Death Valley or Joshua Tree National Park? They are best appreciated in spring when desert blooms offset their austerity and temperatures are still manageable. Early spring—when the gray whale migration overlaps with the end of the elephant seal breeding season and the start of the bird migration—is the optimal time to visit Point Reyes National Seashore. Yosemite is ideal in the late spring because roads closed in winter are reopened, and the park's waterfalls—swollen with melting snow—run fast. Autumn is "crush time" in all the wine destinations, from Napa/Sonoma in the north, central coast, and Temecula in the south. Snowfall makes winter peak season for skiers in Mammoth Mountain and Lake Tahoe, where runs typically open around Thanksgiving. (They sometimes remain in operation into June.)

Climate

It's difficult to generalize much about the state's weather beyond saying that precipitation comes in winter and summer is dry in most places. As a rule, inland regions are hotter in summer and colder in winter, compared with coastal areas, which are relatively cool year-round. Fog is a potential hazard any day of the year in coastal regions. As you climb into the mountains, seasonal variations are more apparent: winter brings snow (at elevations above 3,000 feet), autumn is crisp, spring can go either way, and summer is sunny and warm, with only an occasional thundershower in the southern part of the state.

Microclimates

Mountains separate the California coastline from the state's interior, and the weather can sometimes vary dramatically within a 15-minute drive. On a foggy summer day in San Francisco, you'll be grateful for a sweater—but head 50 miles north inland to Napa Valley, and you'll likely be content in short sleeves. Day and nighttime temperatures can also vary greatly. In August, Palm Springs's thermometers can soar to 110°F at noon, and drop to 75°F at night. Temperature swings elsewhere can be even more extreme. Take Sacramento: On August afternoons the mercury hits the 90s and occasionally exceeds 100°F. Yet as darkness falls, it sometimes plummets to 40°F.