A ‘thermal dome’ to bring high temperatures and dangerous heat to California

A significant early-season heat wave is expected to ravage much of inland California this week, with temperatures reaching 100 from the Sacramento Valley to the Antelope Valley — dangerously high temperatures that according to experts, could pose health risks as nighttime cooling will be limited in many areas.

Much of the western United States is bracing for the effects of a ridge of high pressure, or heat dome, that will begin warming the region on Tuesday, likely sending temperatures to near or record levels, with several watches and excessive heat warnings. already issued.

In Southern California, the most extreme temperatures are expected Tuesday through Thursday in the mountains and inland deserts, with Wednesday expected to be the hottest.

“It’s really going to start warming up tomorrow,” National Weather Service meteorologist Joe Sirard said Monday morning. “These temperatures in the lower mountains and deserts will be 15 to 17 degrees above normal for this time of year.”

High temperatures in the Antelope Valley are expected to reach 103 to 108 degrees Wednesday and Thursday, while valleys in Los Angeles County are expected to peak around 90 degrees. Statewide, the coast will generally avoid the worst of this heat wave, with Los Angeles beaches remaining in the 70s and 80s this week.

Lancaster and Palmdale are expected to tie or break daily high temperature records, Sirard said, with all-time highs topping out at 104 degrees in both cities. An excessive heat watch has been issued for Wednesday and Thursday for the Antelope Valley and surrounding foothills, along with a warning of “dangerously hot conditions” for the Apple and Lucerne valleys, where temperatures may reach 106 degrees.

National Weather Service officials are focusing on the serious and even deadly health effects of extreme heat, especially for vulnerable populations, such as the elderly or pregnant women. The weather service reminds residents in these hot spots to stay hydrated, avoid the sun and heat of the day and use air conditioning.

The heat is also expected to lead to an increase in fires across the state.

Last weekend, the Golden State likely saw its most intense fire activity so far this year, with a 14,000-acre fire in San Joaquin County temporarily forcing evacuations. Several other small fires broke out across the state, including two wildland fires in Santa Barbara County and one in Riverside County.

The most extreme heat this week is expected near the California-Nevada border, where an excessive heat warning will be in effect Wednesday through Friday, with temperatures dangerously high. Forecasters warned of temperatures reaching 115 degrees around Lake Mead and Lake Havasu City, 114 degrees in Las Vegas and up to 120 degrees in Death Valley.

“As the heat increases day by day, there will be little relief overnight, especially in the Las Vegas Valley and Death Valley National Park,” the warning states.

The excessive heat warning will also be in effect in the Mojave Desert Wednesday and Thursday, where “dangerously hot conditions” are expected to bring temperatures between 96 and 106 degrees. In the San Joaquin Valley and lower Sierra Nevada foothills, maximum temperatures are expected to peak between 103 and 108 degrees.

In Northern California, the heat wave is expected to hit even sooner, with heat warnings going into effect Tuesday morning, including in the Sacramento and San Joaquin valleys and the Sierra foothills, where excessive heat warnings were issued. The mercury there is expected to reach 95 to 108 degrees, and “limited nighttime relief, with low (nighttime) temperatures in the 60s to mid-70s,” the warning said.

In the inland North and East Bay and mountains of Sonoma County, high temperatures are expected to reach near 100 degrees Tuesday, Wednesday and Thursday, with nighttime temperatures only falling into the 60s and 70s, according to the heat advisory issued for this region.

“There is a moderate to high risk for those who are sensitive to heat, especially those without effective cooling or adequate hydration,” the National Weather Service Bay Area warned.

Widespread warming will also increase snowmelt, raising concerns about cold, fast-moving waterways across the state, creating what weather services have warned could be “potentially dangerous conditions for those seeking relief in rivers and lakes.

The upper-level high pressure system causing this heatwave is expected to slowly weaken and move eastward by the end of the week, Sirard said.

“By Friday, temperatures start to cool off a little bit,” Sirard said. “We expect a gradual cooling through the weekend,” with more seasonal temperatures expected by Sunday.