The San Francisco Bay Area is facing its first major heatwave of the season, bringing dangerous temperatures and elevated fire risks heading into the weekend.

According to the National Weather Service (NWS), a strong high-pressure system is moving over California, triggering a dramatic spike in temperatures, particularly across inland and elevated areas. Temperatures are expected to reach the upper 90s to low 100s in parts of the East Bay, South Bay, and North Bay starting Friday, May 31.

Heat Advisory Issued for Multiple Bay Area Regions

The NWS has issued a heat advisory from 11 a.m. to 8 p.m. on Friday for several Bay Area locations. These include:

  • Inland areas of Contra Costa and Alameda counties

  • Santa Clara Valley, including San Jose

  • The Santa Cruz Mountains

  • Interior Napa and Sonoma counties

This marks one of the most abrupt warmups the region has seen in over two decades, with cities like Livermore potentially seeing a 20-degree jump in a single day.

Health Hazards: Who Is Most at Risk?

With this rapid rise in heat, health officials are urging caution, especially for vulnerable populations. Those at highest risk include:

  • Seniors and young children

  • Unhoused individuals

  • Outdoor laborers

  • Pets and livestock

Daytime highs will offer little relief, and overnight lows in the 60s will keep the region unusually warm through early Saturday. Experts advise limiting outdoor activity, staying well-hydrated, and checking in on neighbors who may need assistance.

Increased Wildfire Risk Across Dry, Windy Areas

In addition to the heat, fire danger is expected to spike, especially in grassy hillsides and forested zones. The combination of hot temperatures, low humidity, and dry vegetation creates ideal conditions for wildfires.

While winds aren’t predicted to be especially strong, even light gusts paired with dry fuel could spark fast-moving fires. Authorities are asking the public to avoid any outdoor burning, use extreme caution with power tools, and report any signs of smoke immediately.

When Will Relief Arrive?

The peak of the heatwave is expected to hit Friday afternoon, with slightly cooler temperatures Saturday and a more noticeable drop starting Sunday. By early next week, the Bay Area should return to seasonable norms in the 70s and 80s for most regions.

Safety Tips During the Heatwave

To stay safe during the heat event, residents are encouraged to:

  • Drink plenty of water, even if not thirsty

  • Avoid strenuous activity during the hottest hours (typically 12–6 p.m.)

  • Wear lightweight, light-colored clothing

  • Never leave children or pets in vehicles

  • Seek out cooling centers if your home lacks air conditioning

Local cities are also preparing to open cooling centers and deploy outreach teams to help protect the most vulnerable residents.

Final Thoughts

The Bay Area’s early-season heatwave is more than just uncomfortable — it’s potentially dangerous. With elevated fire danger and serious health risks on the rise, preparedness is key. Stay alert, follow local advisories, and take steps to protect yourself and your community as temperatures climb.