Bay Area Faces First-Ever Extreme Cold Warning as Temperatures Plunge Overnight

The National Weather Service has issued its first-ever “extreme cold warning” for the eastern Santa Clara Hills and a cold weather advisory for much of the Bay Area Thursday night and Friday morning.

Temperatures in the South Bay and inland valleys are forecast to drop into the mid-20s and low-30s overnight. National Weather Service meteorologist Dalton Behringer said the cold snap follows a recent atmospheric river, as clearing skies allow heat to escape the atmosphere more efficiently.

This shift marks a change in weather messaging, Behringer said, with the new “extreme cold” designation moving away from agricultural terminology to focus on broader human health risks.

“While some people may see this and say 32 degrees is not extreme cold. For us in the Bay Area, it can be dangerous, especially for people experiencing homelessness,” Behringer said. “Infrastructure and people are not built for this here.”

Meteorologists are advising commuters to allow extra time on Friday morning to scrape frost off windshields and are urging residents to protect the “four Ps”: plants, pipes, people and pets. Behringer noted the hills may remain slightly warmer than valley floors because of a warm air mass aloft, but the risk of frost remains high.

The life-threatening drop in temperature has prompted Santa Clara County’s Office of Emergency Management to activate its cold weather response.

Charles Harris, with the county’s emergency office, said officials are working closely with public health and supportive housing departments to reach those most at risk. While the county cannot mandate that individuals move indoors, outreach teams are working to distribute survival gear to unhoused encampments through the evening.

“We give out emergency blankets, we give out water, tents, tarps, blankets,” Harris said. “As a county, we can’t force people into housing, but we can meet them where they are.”

The county is operating eight warming centers, Harris said. In San José, the city has activated additional locations, including community rooms and libraries. The sites serve as temporary shelters during the cold weather, providing access to warm food and restrooms overnight before returning to normal public use during the day.

Beatriz Ramos, chief programs officer for HomeFirst, said teams are targeting specific geographic areas, including southern and western portions of San José. HomeFirst operates overnight warming locations at sites such as the Roosevelt Community Center and the Evergreen Library. While the sites are typically referral-based, Ramos said entry requirements are relaxed during inclement weather activations.

“Currently, we do have a full program with a waitlist. However, if someone comes to the door, they would not be turned away,” Ramos said. “We would work for them to ensure that they have safety and protection against the elements for the night.”

Ramos said larger facilities, like the Boccardo Reception Center, have 250 beds and can increase capacity during emergencies. If a specific site is full, staff coordinate transportation to other shelters within the network.

Infrastructure officials are also on alert. Liann Walborsky, with San José Water, said the utility’s operations team is prepared for potential main breaks, noting local water mains are buried deep enough to provide natural insulation. Because water moves continuously through most of the system, that flow helps prevent freezing. The county roads department said it will monitor for hazards such as black ice.

County officials are coordinating with PG&E to monitor the power grid as residents increase heater use through Friday morning. Harris encouraged residents to sign up for AlertSCC to receive ZIP code-specific emergency notifications and urged the public to avoid using open flames or stoves to heat homes.

Along the coast, California State Parks rangers and lifeguards are monitoring conditions as a high surf advisory remains in effect through Friday night. In the Sonoma-Mendocino Coast District, beaches from Russian Gulch to Doran Park remain closed because of a recent sewage spill in the Russian River. State Parks officials have also closed the Goat Rock gate at Sonoma Coast State Park to deter beach access in an area prone to strong backwash and sleeper waves.

Safety officials are urging visitors to view large surf only from paved parking lots and to avoid steep beaches, including Wrights Beach, Portuguese Beach and Schoolhouse Beach.