Dangerously hot conditions are expected, with inland temperatures up to 110 and highs of 95 along the coast, according to the National Weather Service.
Overnight lows will range from the lower 70s to lower 80s.
The excessive heat warning, effective through tomorrow night, covers North Bay interior areas and coastal ranges; the San Francisco Bay shoreline; interior East Bay areas; Santa Clara County; the Santa Cruz Mountains; and interior Monterey County.
A heat advisory has also been issued for other parts of the Bay Area, including coastal areas, tonight through 11 p.m..
A fire weather watch has been issued for parts of Southern Monterey County, from tomorrow morning 6 a.m. until 8 p.m. Thursday.
The Weather Service said: "Critically dry fuels and gusty offshore winds will lead to increased chances for fire starts and fire spread.”
During the heat wave, people and pets should not be left in cars without air conditioning, and outdoor activities should be limited for those who are sensitive to heat, and people should stay hydrated.
High temperatures and light winds, combined with vehicle exhaust, will result unhealthy air quality around the Bay Area for the next two days, air district officials said.
