Hint of summer to arrive as Bay Area temperatures set to rise

The first and last days of the work week are expected to be the two hottest as high pressure builds and the Bay Area gets a hint of summer during the first week of June.

It’s only a tease, according to the National Weather service. Come the weekend, coastal drizzle may be back and temperatures in the hottest places are expected to be back in the 60s and 70s.

“On Tuesday, that high pressure starts to break,” NWS meteorologist Brayden Murdock said Monday. “We’ll start to see things cool off by a few degrees, the off-shore flow will begin again, and the marine layer will start to return.”

Such has been the routine for what has been a span of a couple of months. The high-pressure increases that have given rise to higher temperatures have not sustained themselves, and often have been followed by significant drops in the barometric pressure and the onset of clouds and occasional rain.

Such a pattern is not that unusual for this time of year, according to the weather service.

“The jet stream generally this time of year stays off to the north, and so the high pressure builds and decreases as the jet stream flows,” Murdock said. “We’re kind of in that in-between area right now, where the conveyor belt of the jet stream doesn’t go right through our area. Usually, we don’t see the jet stream shift and give us a chance for those significant long-tem high pressures until late in the summer and early in the fall.”

As it is, this high-pressure increase already had lifted some temperatures in the interior East Bay into the mid-80s by Monday afternoon, and they were expected to peak at least in the high 80s. The hottest spots in the South Bay were expected to reach the mid-to-low 80s, the weather service said.

Those temperatures are expected to decrease by 6-8 degrees on Tuesday, before they gradually build again through Friday, when they are forecast to peak about 3-4 degrees higher than they are on Monday, with the interior East Bay reaching the 90s and the South Bay tickling the upper 80s.

A 10-12 degree cooldown is then expected to follow on Saturday.

Closer to the water, the heat-up is not expected to come at all. Oakland is expected to max at 69 degrees on Monday and 73 on Friday, as is San Mateo. San Francisco’s high is forecast to be 66 on Monday and 68 on Saturday.