LIVERMORE, Calif. (KGO) — An excessive heat warning is in effect for the San Francisco Bay Area through Wednesday afternoon, according to the National Weather Service. It was updated from a heat advisory early Monday.

“We will see temperatures similar to the much, much hotter summer temperatures here,” said Michael Stanton, a public health professor at CSU East Bay. “As much as it feels like when you look at the calendar and see October, we have to take precautions like it’s the middle of summer in the Bay Area.”

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Although October begins Tuesday and fall is in full swing, triple-digit conditions are expected across the East Bay this week.

“Stay hydrated because you won’t even notice if you become dehydrated,” Stanton said. “Try to stay indoors or in the shade as much as possible and avoid strenuous activity.”

And the heat is already affecting air quality.

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The Bay Area Air District issued a “Spare the Air Alert” for Monday due to high inland temperatures and weak winds. Now it has been extended until Tuesday.

“So in certain parts of the Bay Area we have the possibility of reaching triple digits, and when the winds are light, there isn’t enough energy there to emit the pollutants that come from the millions of cars and exhaust on the streets of the Bay Area will arise,” Ralph Borrmann, a spokesman for the Bay Area Air District, said.

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That means the Air Quality Management District is encouraging people across the Bay Area to protect their health by avoiding outdoor activities during the hottest part of the day.

“We suggest that people exercise early in the morning as early as possible on these poor air quality days. “Simply reduce driving or other environmentally harmful activities as much as possible, then that will be the biggest help,” says Borrmann.

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In the meantime, PG&E warns of power outages due to strong winds and drought for 11 counties, four of them in the Bay Area.

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It may impact portions of Alameda, Contra Costa, Napa and Sonoma counties.

Doctors are also advising people to make sure they wear appropriate clothing that covers their skin during this heat wave and to ensure that no children or pets are left in the car.