A second straight day of hot weather was set to settle in on the Bay Area on Tuesday, according to the National Weather Service, with a significant cooldown waiting on deck. Then, following a couple of days of that, some more, less intense, heat will arrive. Then it will cool off almost immediately.

“It’s a little bit of roller coaster temperature-wise,” NWS meteorologist Matt Mehle said.

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The second major upward tick was expected to bring temperatures in the hottest spots Tuesday into triple digits and the upper 90s. Brentwood is expected to max at 100, Livermore at 98 and Concord at 96.

Come Wednesday, those same temperatures were expected to be 83, 80 and 77, respectively.

The heat already was set to sizzle less in other places Tuesday. San Jose is expected to reach 92, along with Morgan Hill, figures that are expected to lead the South Bay. Temperatures near Oakland are expected to max in the low 80s and high 70s, while San Francisco is expected to reach 76.

On Wednesday, San Jose won’t reach 80, Oakland won’t reach 70 and San Francisco won’t reach 65, according to the weather service.

A heat advisory remained in effect for the East Bay hills and interior valleys through 8 p.m. on Tuesday. The advisory for the Santa Cruz Mountains, Santa Clara Valley and Eastern Santa Clara Hills were no longer in effect.

“We’ve definitely had bursts of heat at the end of September and the beginning of October in the past,” Mehle said. “So this is definitely not uncommon to have one last round of heat.”

The heat Tuesday may not be the final round, either. Temperatures are expected to warm up into the mid to upper 90s in the hottest spots again by Friday, as more high pressure replaces the trough.

“We’re going to be about 10-15 degrees cooler from Tuesday to Wednesday,” Mehle said. “That’s not going to say Wednesday is going to be cold. It’s just a return to normal temperatures. It should be great weather.

The arrival of the trough from the Pacific Northwest is expected to bring with it a return of the marine layer, which first was squished then eroded over parts of the ocean during the recent heat up. The marine layer brings with it a cloud layer and an on-shore breeze that keeps the region cooler.

When it returns, the marine layer is expected to be thick enough to reach areas of the East Bay.

“It’s sneaking up the coast right now,” Mehle said.

It’s influence is expected to remain even as temperatures soar again Friday. That increase is expected to last only one day, with temperatures expected to be back in the high 80s in the hottest places on Saturday.