Wednesday’s drop is likely to be dangerous given a weather pattern that a National Weather Service meteorologist described as a “temperature roller coaster.”

That doesn’t mean the hot weather is finally coming to an end this year.

“It will be about 10 to 15 degrees cooler Tuesday through Wednesday,” meteorologist Matt Mehle said Tuesday. “That doesn’t mean Wednesday will be cold. It’s just a return to normal temperatures. It should be great weather.”

All of this is like saying that the little hills on the roller coaster are “easier” than the long, high drops straight to the ground. Temperatures are not expected to exceed 85 degrees anywhere in the region on Wednesday. A heat advisory in effect for the East Bay Hills and Inland Valley was set to expire Tuesday at 8 p.m.

The cooling process had already begun in certain parts of the region on Tuesday. In San Jose, the temperature was 90 degrees at midday and was expected to peak at 92 degrees, making Morgan Hill the hottest spot in the South Bay. They peaked at 95 on Monday.

Temperatures in and around Oakland were around 76 degrees midday and are expected to peak around 80 degrees, similar to San Mateo (78, 81) along the peninsula. San Francisco also recorded 75 at midday and is expected to reach 78. Those temperatures were accompanied by humidity above 50%, the weather service said, making it slightly uncomfortable but much cooler than the Far Eastern Bay.

Temperatures were boiling inland. At noon in Brentwood, the gauge read 92, on the way to the expected 100. In Livermore, it read 95, where 99 was forecast. In Concord, the midday temperature was 91 and was expected to peak at 97. In Pleasanton it was 95 and will probably be 97.

“We have had heat outbreaks in late September and early October in the past,” said Mehle. “So it’s definitely not unusual for there to be one last round of heat.”

Next comes the jump.

On Wednesday, Livermore will not rise above 85, Concord and San Jose will not reach 80, Oakland will not reach 70 and San Francisco will not exceed 65, the weather service said.

Those numbers will rise again starting Thursday, and are expected to sizzle again on Friday, with the weather service predicting the hottest places in the East Bay will reach the high 90s again and the hottest places in the South Bay will reach the middle will fly over -90s.

This warm-up is expected to be followed by more moderate temperatures on Saturday, similar to those on Wednesday. The arrival of a trough from the Pacific Northwest will bring with it the marine layer that has been eroded and crushed by the high pressure that caused the recent heat.

The return of the marine layer and the weakening of high pressure that will reassert itself amid the trough will combine to keep the onset of late week heat at cameo levels, Mehle said.

“I expect the weekend to be the weather that will make people want to move here,” he said.

Originally published: September 24, 2024 at 7:33 am