Bay Area warm-up to send SF temperatures into the mid-80s

From left: Amilia Madigan, age 11, and her mother Desy Stoyanov cool off from the heat using the water sprinklers at Golden Gate Park on Friday, Sept. 1, 2017, in San Francisco, Calif. The Bay Area is expected to heat up again, reaching the low 90s in some parts of the East Bay and South Pay. less From left: Amilia Madigan, age 11, and her mother Desy Stoyanov cool off from the heat using the water sprinklers at Golden Gate Park on Friday, Sept. 1, 2017, in San Francisco, Calif. The Bay Area is expected ... more Photo: Santiago Mejia, The Chronicle Buy photo Photo: Santiago Mejia, The Chronicle Image 1 of / 38 Caption Close Bay Area warm-up to send SF temperatures into the mid-80s 1 / 38 Back to Gallery

Get ready to feel the heat — again.

Forecasters expect temperatures to rise in the Bay Area on Tuesday and Wednesday, reaching the mid-80s in San Francisco and low 90s in parts of the East Bay and South Bay.

The warm-up is expected to be more uniform throughout the region compared to other heat waves this summer that brought wildly varied temperatures, according to Roger Gass, a meteorologist with the National Weather Service.

“Things like 105 inland are not expected this time,” he said. “It’s more of a mid- to upper 80s, closer to 90s event, and we’re not expecting huge variation in the Bay Area.”

The latest hike in temperatures is the result of a high-pressure system moving in from the eastern Pacific Ocean, Gass said. The new system is pushing inland a front that brought cooler weather to the Bay Area in recent days and is causing winds to blow toward the coastline instead of in from the ocean, he said.

“That change in direction cuts off our natural-occurring air conditioning,” Gass said.

Temperatures in San Francisco are expected to cool slightly after Wednesday, though the city will still see temperatures in the 80s on Thursday.

The San Francisco Department of Public Health tweeted an advisory Monday instructing people to stay inside with air conditioning on when possible — especially vulnerable populations, including infants, young children and the elderly.

A heat wave over the Labor Day weekend this month set record temperatures for around the Bay Area. In downtown San Francisco, thermometers hit 106 degrees on Sept. 1, breaking the previous record of 103 set on June 14, 2000. On Sept. 2, San Francisco hit 101, making it the third time the city had seen back-to-back days of triple-digit heat since 1874.

The sweltering weather was suspected of causing the deaths of six people in the Bay Area, three in San Francisco and three in San Mateo County. All six were elderly. In San Francisco, all three lived alone and 911 call records show that none had called for medical help before their bodies were discovered.

The San Francisco medical examiners office said it was likely that the three victims in the city died of heat-related causes. San Mateo County confirmed that the other three victims died of shock caused by heatstroke.

Annie Ma is a San Francisco Chronicle staff writer. Email: ama@sfchronicle.com Twitter: @anniema15