The Western United States baked through the unofficial end of summer, as temperatures in some parts threatened to peak Saturday at levels not seen in decades and wilting heat challenged crews battling wildfires across the region.

Areas inland from the San Francisco Bay Area could reach 115 degrees, a temperature last seen in 1950, forecasters said. Temperatures in Sacramento were expected to shoot past 110.

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While triple-digit highs in Southern California were forecast to drop into the 90s over Labor Day weekend, the heat created difficulties for crews fighting a wildfire just north of downtown Los Angeles.

Several hundred firefighters worked to contain a blaze that chewed through brush-covered mountains, prompting evacuation orders for more than 600 homes in Los Angeles, Burbank and Glendale.

No injuries have been reported, and one home has burned, officials said. At nearly 8 square miles (21 square kilometers), the fire was the largest in the city’s history, Los Angeles Mayor Eric Garcetti said.

Fire officials said that if winds do not pick up, they were confident they could confine the fire to slopes that have not burned in several decades.

The warmth extended up the West Coast and into mountain states, with excessive-heat warnings posted for southwest Oregon and lesser advisories in northwest Oregon.

Fire weather warnings were in effect for parts of Wyoming, South Dakota and Montana, where a fire was burning in Glacier National Park.

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Western Washington state expected a sunny, hot and dry holiday weekend. A fire about 80 miles (129 kilometers) southeast of Seattle has burned more than 23 square miles (60 square kilometers) and led to new evacuations notices Saturday.

The weeklong heat wave was generated by high pressure over the West, the National Weather Service said.

Forecasters said more heat could be expected when remnants of Tropical Storm Lidia move north from Mexico’s Baja California during the weekend.

In Northern California, the extreme heat sent Michelle Ogburn to a cooling center set up in Santa Clara’s North Branch Library, one of many that were opened throughout the state.

Ice-water stations were set up and dozens of people, many of them homeless, took shelter Friday.

“I work from home and I live in an old mobile home with no air conditioning and not very good insulation,” said Ogburn, who lives in Sunnyvale. “Today it was very hot and I just couldn’t work.”

Managers of California’s power grid asked for voluntary electricity conservation. Tens of thousands of people across the state were without power at various times Friday, though most outages didn’t last long.

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