Although temperatures remain relatively constant, there are two definite seasons—wet and dry—with more than 80 percent of annual precipitation taking place between November and March. Perhaps the most distinctive feature of the local climate is the banks of fog that can roll in off the ocean, quickly covering various areas of the city, and then disappear just as quickly. The fog is most common on summer mornings, coming off the cooler ocean and backing up against the hills, but it also comes from the colder inland areas during the winter. The fog affects different elevations in varying amounts, covering the city in complex patterns of fog and sunshine.
NORTHERN CALIFORNIA'S EAST BAY
The Bay Area saw further growth in the decades following World War II, with the population doubling between 1940 and 1960, and doubling again by 2000. The 1937 completion of the Caldecott Tunnel through the Berkeley Hills fueled growth further east, where there was undeveloped land. Cities in the Diablo Valley, including Concord and Walnut Creek, saw their populations increase tenfold or more between 1950 and 1970. The addition of the BART commuter rail system in 1972 further encouraged development in increasingly far-flung regions of the East Bay. Today, the valleys east of the Berkeley, Oakland and Hayward hills contain large affluent suburban communities such as Walnut Creek, San Ramon and Dublin. These areas remain largely white demographically.
The East Bay is not a formally defined region, aside from its being described as a region inclusive of Alameda and Contra Costa counties. As development moves generally eastward, new areas are described as being part of the East Bay. In 1996, BART was extended from its terminus in Concord to a new station in Pittsburg, incorporating the newly expanded Delta communities of Pittsburg and Antioch as extended regions of the East Bay. Beyond the borders of Alameda County, the large population of Tracy is connected as a bedroom community housing commuters traveling through to or through the East Bay.
Except for some hills and ridges which exist as parklands or undeveloped land, and some farmland in eastern Contra Costa and Alameda Counties, the East Bay is highly urbanized. The East Bay shoreline is an urban corridor with several cities exceeding 100,000 residents, including Oakland, Hayward, Fremont, Richmond, and Berkeley. In the inland valleys on the east side of the Berkeley Hills, the land is mostly developed, particularly on the eastern fringe of Contra Costa county and the Tri-Valley area. In the inland valleys, the population density is less and the cities smaller. The only cities exceeding 100,000 residents in the inland valleys are Antioch and Concord.
- East Bay cities include:
- Alamo (unincorporated community)
- Bay Point (unincorporated community)
- Canyon (unincorporated community)
- Castro Valley (unincorporated community)
- El Cerrito
- El Sobrante (unincorporated community)
- Kensington (unincorporated community)
- North Richmond (unincorporated community)
- Pacheco (unincorporated community)
- Pleasant Hill
- Rodeo (unincorporated community)
- Saranap (unincorporated community)
- San Leandro
- San Lorenzo (unincorporated community)
- San Ramon
- San Pablo
- Sunol (unincorporated community)
- Union City
- Walnut Creek