Berkeley packs one of the Bay Area's sharpest climate gradients into a city only a few miles across. The flatlands along the bay see marine layer fog on many summer mornings, with afternoon highs around 70°F, and get about 25 inches of rain a year. The hills above UC Berkeley climb to about 1,750 feet at Grizzly Peak. On mornings when the marine layer is shallow, they sit above the fog, and they get 26 to 29 inches of rain a year. The Berkeley Hills weather divide is one of the clearest examples of Bay Area microclimates at the scale of a single city.
What Is Berkeley's Summer Weather Like?
Berkeley summers often start cool and gray in the flatlands. On most summer mornings, the marine layer pushes through the Golden Gate and across the bay. It brings low clouds and temperatures in the 50s to the waterfront and the western half of the city. By early afternoon the fog usually burns off, and the flatlands warm into the upper 60s and low 70s. When the marine layer is shallow, the hills above the Claremont Hotel and North Berkeley rise above it and get sunshine from morning on.
Heat waves hit Berkeley less hard than inland cities. When Livermore reaches 105°F and Concord 100°F, the Berkeley flatlands might see the 80s or low 90s, while the marina and waterfront stay cooler. Berkeley sits directly across the bay from the Golden Gate, so cool ocean air reaches it easily whenever the sea breeze blows. Even in strong heat waves, Berkeley rarely stays extremely hot for more than two or three days.
How Much Rain Does Berkeley Get?
Berkeley's rainfall rises steadily as you climb into the hills. The flatlands and campus average about 25 inches a year, a little more than San Francisco. The hills above campus get 26 to 29 inches, and Tilden Regional Park near the ridge averages about 26. The difference comes from orographic lift, as Pacific storms push moist air up the west-facing hills and squeeze out extra rain. In a single big storm, you can see the difference between downtown Berkeley and the hill neighborhoods.
Nearly all of the rain falls between November and March. Winters are mild, with highs in the upper 50s and lows in the low to mid 40s. Frost is rare in the flatlands, but it can form in sheltered hill canyons on clear, calm nights when cold air drains downhill. Berkeley's flood risk centers on Strawberry Creek and the other urban creeks that drain the steep hills, especially during intense atmospheric river storms.
What Is Fire Weather Risk in the Berkeley Hills?
The Berkeley Hills are in one of the highest fire-risk zones in the Bay Area. Steep terrain, dense stands of eucalyptus and Monterey pine and dry fall Diablo winds together can produce catastrophic fires. In October 1991, the Oakland Hills fire, also called the Tunnel Fire, burned 1,520 acres just south of Berkeley. It destroyed 2,843 single-family homes and 437 apartment and condominium units and killed 25 people. Hot, very dry northeast winds gusting to about 65 mph drove the flames.
Red Flag Warnings for the Berkeley Hills are most common from September through November, when dry plants, warm weather and offshore winds line up. Residents of the hill neighborhoods along the wildland edge should watch fire forecasts closely during fire season and keep evacuation plans ready. The narrow, winding hill roads can jam during an evacuation, as the 1991 fire tragically showed.
When Is the Best Weather in Berkeley?
September and October are Berkeley's best weather months, because the summer fog retreats before the rains begin. The flatlands warm into the low to mid 70s, and the hills are warm and clear. Sunshine is most reliable across the whole city, from the marina to the ridge, in these two months. April and May are also excellent, with green hills, wildflowers in Tilden Park and fewer foggy days than summer.
Berkeley's weather rewards people who think about how high up they will be. A foggy, 60-degree morning in the flatlands can be a sunny, 70-degree morning in the hills, only a 10-minute drive away. The campus sits in the transition zone, where the fog often hangs at the level of the eucalyptus groves. Knowing how high you will be and whether the fog has lifted yet is the key to dressing right and planning your day.
