Records To Fall As Heat Dome Makes SoCal Hottest Place In U.S.

LOS ANGELES, CA — Summer doesn't officially start for nearly two weeks, but much of the Southland is under an excessive heat watch as a heat dome brings record triple-digit temperatures to wide swaths of the Southwest.

Notable for soaring temperatures 20 degrees above normal, the first major heatwave of the year is largely sparing the Southern California coastline while baking inland communities. The National Weather Service issued excessive heat warnings for Riverside County and 17 million others in California, Arizona, Nevada and Utah.

The warnings mean dangerous and possibly life-threatening heat is expected. The excessive heat warnings were issued for Wednesday morning through Friday evening for the Mojave Desert, the Coachella Valley, the Antelope Valley and Southwest Riverside County.

“Temperatures well above average for the time of year — some spots as much as 10 to 20 degrees above average,” said Marc Chenard, a weather service meteorologist. He said unseasonably hot weather was expected to spread northward through California to the Pacific Northwest.

The heat is expected to increase the wildfire risk, especially in Central and Northern California, where the Corral Fire is burning.

California was the hottest place in the country Tuesday with 112 degrees at Furnace Creek in Death Valley, 108 degrees in Needles and 104 degrees in Palm Springs. Such temperatures don't usually bake the Southland until July.

According to the weather service, temperatures are expected to climb throughout the week, peaking in Palm Springs on Thursday at 111 degrees. Death Valley is expected to reach 120 degrees. Several of the anticipated daytime highs are expected to break heat records for this time of year.

In addition to high temperatures, the heat dome effect is creating a stark divide between the coast and inland communities. Just 102 road miles separate Newport Beach and Palm Springs, but the desert oasis will be about 40 degrees hotter than the beach on Thursday, according to the National Weather Service.

From Malibu to San Diego, coastal highs are expected to hover in the low 70s under cloudy conditions all week. In between, cities such as Los Angeles and Temecula can expect temperatures to be 5 to 10 degrees warmer than normal this week. Thursday's high in Northridge is expected to be 86 degrees Thursday, 85 degrees in Temecula, 82 degrees in Santee, and 80 degrees in Rancho Santa Margarita.

"A hot air mass will remain in place across the interior valleys for much of this week, with temperatures well above normal for this time of year," forecasters said. "Closer to the coast, the warming trend will be moderated due to persistent night through morning low clouds and fog and a moderate to strong onshore flow."

Forecasters issued their standard warnings for excessive heat, reminding people to drink plenty of liquids, stay indoors as much as possible and avoid leaving children or pets in vehicles.

"Take extra precautions when outside. Wear lightweight and loose-fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke," forecasters said.

The heat prompted the U.S. Border Patrol to issue a warning on Monday after it confirmed that four migrants died last weekend from heat-related causes while attempting to cross into the country.

Cooler conditions are expected to return by Friday into Saturday.

City News Service and the Associated Press contributed to this report.