PHOENIX — Much of the West was smothered in a blanket of heat Saturday with triple-digit temperatures expected from Phoenix to Los Angeles.

Above-normal temperatures were expected through the weekend as a high-pressure system centered over New Mexico acted like a lid to block cooler air, leaving valleys, deserts and mountains high and very dry.

Authorities warned people not to leave small children or pets in cars.Los Angeles and other cities were keeping libraries and other facilities open late to serve as cooling shelters.

Phoenix broke a daily record Friday, reaching 117 degrees, and the expected Saturday high of 116 would top a 1992 record by 4 degrees, National Weather Service meteorologist Dan Leins said.

“Stay inside if you can,” he said. “It’s dangerous, regardless of how acclimated you are to the climate, because it can be deadly.”

Mike Stephens took precautions for an early-morning run in Estrella Regional Park, a desert and mountain wilderness area in Phoenix. He carried 1 1/2 liters of water and was careful not to overdo it.

“You have to know what your body can do,” he said.

The weather service issued warnings of excessive heat throughout Southern California into Saturday night, with some areas expected to see highs of 10 to 15 degrees above normal, said Scott Sukup, a weather service meteorologist in Oxnard.

A high of 95 was forecast for downtown Los Angeles, with the San Fernando Valley and other inland valleys ranging up to 108. Palm Springs could hit 117 and Death Valley’s high could reach 120 to 125, according to the weather service.

Highs of 110 to 112 were projected for Las Vegas and the Mojave Desert.

“There’s been a big area of high pressure that was over New Mexico and it’s been expanding westward,” Sukup said.

The heat, coupled with low humidity, has increased the fire danger in California, where some two dozen major fires in recent weeks have destroyed thousands of acres of trees and brush left bone-dry by years of drought.

About 1 million people were expected to hit 32 miles of Los Angeles County beaches this weekend, county lifeguard Capt. Kenichi Haskett said.

But they might have to share the ocean with barb-tailed stingrays drawn to the calm, warm waters.

“We could have a couple of hundred at Santa Monica Bay,” he said.

About two dozen people were stung Thursday and Friday, he said.