A heat dome will send temperatures into the triple-digits across the West as fires burn

By Mary Gilbert, CNN Meteorologist

(CNN) — Daily temperature records will tumble as sizzling early season heat from a summerlike heat dome sends thermometers skyrocketing into the triple digits in parts of California and the West this week.

The official start of summer is just a few weeks away, but it will feel like July in much of the West as temperatures climb 20 degrees or more above average, the highest temperatures of the year so far for many locations.

Excessive heat warnings are in effect for more than 17 million people in California, Nevada, Utah and Arizona this week. The warnings are the most extreme form of heat alert issued by the National Weather Service and are used when widespread, dangerous heat is expected.

The soaring temperatures are being caused by a heat dome, a large area of high pressure that parks over an area, traps air and heats it with abundant sunshine for days or weeks. The resulting heat becomes more intense the longer a heat dome lasts.

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Dangerous heat will get underway Tuesday afternoon in parts of California and expand its reach into more of the Southwest by Wednesday and as a heat dome parks over the West. It will then reach the Pacific Northwest by late-week. The most extreme heat will avoid major population centers along the coast, but Los Angeles will still be 5 to 10 degrees warmer than normal this week.

Temperatures will soar into the upper 90s and low 100s Tuesday in California’s Central Valley – including where the Corral Fire is burning near Tracy.

Sacramento is forecast to hit triple digits Tuesday for the first time this year. California’s capital typically hits this threshold in early June, but last year it didn’t happen until the end of the month.

Triple-digit temperatures will become widespread in the Central Valley Wednesday and stick around into the weekend. Conditions will also sizzle in Southern California’s desert regions.

Death Valley, the hottest place in the world, is likely to reach a high temperature of at least 120 degrees by Thursday. Even the brutal desert landscape doesn’t typically get this hot until mid-to-late June.

The Southwest will start to bake by Wednesday as temperatures in parts of southern Arizona and far southern Nevada approach 110 degrees.

Phoenix will likely have hit 110 degrees for the first time this year by Thursday even though the city doesn’t typically encounter these temperatures until mid-June. High temperatures are forecast to climb into the low 110s in Las Vegas, more than three weeks earlier than the city typically exceeds this threshold.

The early summerlike heat will threaten daily high temperature records across a significant portion of the West this week.

Phoenix; Las Vegas; Flagstaff, Arizona; Reno, Nevada; and Fresno, California, are just a handful of cities where the day’s high temperature record could fall.

By Friday, records could be broken in parts of Oregon, Washington, Idaho and Colorado as heat expands north and east.

Fire danger will also rise while the heat is at its peak.

Sizzling temperatures and low levels of humidity will dry out short-fuse fuels such as grasses and brush, making them more prone to burn. Breezy winds will develop at times, especially in California into midweek. The combination of these factors will make it easier for fires to ignite and spread.

Corral Fire blazing in California’s Central Valley

The Corral Fire has consumed more than 14,000 acres of land in California’s San Joaquin county since it ignited south of Tracy Saturday afternoon.

Residents were ordered to evacuate over the weekend as the fire – initially fueled by gusty winds and dry, hot conditions – threatened communities.

Firefighters gained an upper hand as winds eased Sunday and Monday and the blaze was 90% contained by Tuesday morning, according to CAL Fire.

Evacuation warnings were lifted Monday evening as containment increased, according to CAL Fire. Officials urged residents to remain vigilant and be ready for potential changes to the fire risk level.

Two Alameda County firefighters were injured while responding to the fire, Cal Fire Battalion Chief Josh Silveira told CNN early Sunday morning. They had minor to moderate injuries and were transported to a local hospital for evaluation and treatment, Silveira said.

A section of I-580 was closed in both directions over the weekend as the fire’s thick smoke enveloped the roadway. All lanes were reopened Sunday night, according to the California Department of Transportation.

The cause of the fire is under investigation, according to CAL Fire.

Gusty winds up to 30 mph are possible Tuesday, which could complicate ongoing containment efforts. Temperatures will also surge well into the 90s from Tuesday through the weekend. An excessive heat warning is in effect for the region from Tuesday through Thursday.

Note: The CNN Original Series “Violent Earth with Liev Schreiber” explores harrowing weather events such as wildfires that are increasingly frequent in our changing climate. It airs on Sundays at 9pm ET/PT.

CNN’s Jillian Sykes and Dalia Faheid contributed to this report.

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