New heat blast for Bay Area will also bring red-flag fire danger

A new weather front will bring warm temperatures and serious fire danger to portions of the Bay Area later this week, weather officials said.

The National Weather Service issued a red-flag warning Tuesday for the East Bay hills and the interior mountains of the North Bay, citing high winds and low relative humidity that could quickly exacerbate any small fire started. The warning is set to last from 11 p.m. Wednesday to 9 a.m. Thursday.

For the rest of the region, the weather pendulum that keeps swinging back and forth between cool conditions mirroring the late fall and early winter and warm conditions that are more in keeping with late spring and summer is about to head toward hot again.

“We’ve got the pattern change in full swing,” National Weather Service meteorologist Karleisa Rogacheski said. “We’ve got high pressure building over the West, and the low-pressure trough is moving east. That will allow for some warming and drying with some off-shore winds.”

That’s generally the recipe for the heat, and this time the peak of it is expected to take temperatures in the Bay Area’s hottest places into the high 90s and perhaps the 100s by Thursday. The far East Bay, as well as areas of the North Bay are expected to be the hottest, though areas of the South Bay won’t log far behind. Morgan Hill and Redwood City also may reach the 90s by Thursday, according to the weather service.

Some of the temperatures could rise into record-setting territory, especially along the coastline, Rocacheski said. Cities along the Peninsula and San Francisco itself may rise into the 80s on Thursday.

“We expect Thursday to be the hottest day,” Rogacheski said.

The cooldown in the hottest spots will be gradual. Temperatures are expecteds to remain at least in the 90s in the far East Bay, areas of the South Bay and in the North Bay mountains and interior through Friday. By Sunday, the thermometer in the hottest places is not expected to get much higher than the low 80s.

As for the trough, it brought a bit of drizzle and very light rain to some areas of the region on Monday evening. A few hundredths of an inch fell on some cities near the water, and some rain that wasn’t measurable fell on the interior, according to the weather service.