Heat Risk

'Major Heat Risk' expected to impact Northern California

Amy Graff

After seeing an unusually cool spring and start to summer, Northern California is expected to get some hot weather. 

The National Weather Service warned that “Major Heat Risk” is forecast to impact the region late this week into the holiday weekend.

Gradual warming is predicted through the week across the region, and by Saturday and Sunday, temperatures are expected to be in the 100s in the Central Valley, in the 80s in the Tahoe Basin and in the high 80s to 90s in the inland Bay Area. The heat will likely push into at least July 4.

In some spots, highs will be jumping from 5 to 10 degrees above normal at the start of the week to 10 to 15 degrees above normal over the weekend, meteorologists said. 

“A long awaited pattern change is expected late this week into next weekend,” the weather service’s Bay Area office said in its forecast.

The warmup comes as low pressure associated with cooling exits the area. For weeks, the region has seen low-pressure systems move through, but this pattern is finally ending. High pressure that brings warning is building, expanding “northwestward from northern Mexico towards the West Coast,” the weather service said. 

In the Bay Area, the main increase in temperatures begins Thursday, with gradual warming into the weekend. Friday through Sunday, downtown SF is expected to be in the low to mid-70s, the South Bay in the mid-90s, the East Bay hills close to 90, and the North Bay mostly in the upper 80s, with some low 90s in the northern Napa Valley, said Dalton Behringer, a forecaster with the weather service. Friday and Saturday are expected to be the warmest days of this week.

“It kind of starts to cool off in the Bay Area as we get into next week,” Behringer said. 

The weather service is warning of heat risk in the Sacramento Valley from Friday through Sunday.

“We’re going to start seeing it continuously warming over the next few days,” Sara Purdue, a forecaster with the weather service’s Sacramento office, said. The hottest parts of the valley could see afternoon highs hit 110 degrees. The agency “advised people to consider canceling outdoor activities during the heat of the day.”

In the Tahoe Basin, South Lake Tahoe is forecast to see a high of 79 degrees on Friday and 83 on Saturday and Sunday. “This quick warm-up will be quite the shock given that temperatures have been relatively mild as of late,” the weather service’s Reno office said in its forecast. “So, if your holiday plans take you outside this weekend, remember to stay hydrated and take periodic breaks in the shade or indoors.”

The massive snowpack in the Sierra Nevada will continue to melt in the heat. As of Monday morning, the weather service had not yet issued any special advisories warning of an increased risk of flooding due to snowmelt over the weekend. The agency has warned of increased risk all summer on rivers that are cold and flowing rapidly because of the unusually wet winter.