The heat dome that produced a prolonged and brutal bout of heat in Mexico during May is expanding northward into the western United States. It is poised to bring record-high temperatures from Texas to the Pacific Northwest this week — with some of the most intense heat in Arizona and California’s interior.
Las Vegas, Phoenix and Sacramento all face their hottest weather so far this year and are under excessive-heat warnings.
Wednesday, Thursday and Friday are predicted to be the hottest days — with highs at least 10 to 20 degrees above normal — before the heat shifts location and slightly eases in the hottest spots by the weekend.
Temperatures of 100 to 110 degrees are anticipated in much of the interior West, with some desert locations topping 110 or even 120 degrees. Dozens of record highs are predicted.
Much of interior California, the south and west of Arizona, southern Nevada, as well as southern Utah are under excessive-heat warnings. Parts of South Texas, where extreme heat has been frequent in recent weeks, also placed under heat warnings Tuesday as heat index values — a measure of how hot it feels combining heat and humidity — approach 120 in some locations.
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These heat alerts affect about 34 million residents, and this number could grow as the heat peaks this week.
Areas most affected
The Desert Southwest will experience the most extreme heat. Warnings there take effect Wednesday and include Phoenix; Las Vegas; Death Valley, Calif.; and the surrounding deserts.
California’s Central Valley is also under a heat warning, including Bakersfield, Fresno and Sacramento. The warning takes effect in the northern half of the valley Tuesday, extending as far north as Shasta County and Redding, and expands to the south Wednesday.
Heat advisories affect locations as close to the coast as eastern portions of the San Francisco Bay Area, and these may be expanded.
The Weather Service’s new HeatRisk product, which highlights the regions most susceptible to temperatures that could pose a threat to human health, shows conditions beginning to ramp up Tuesday before a leap toward widespread “major” — or Level 3 out of 4 — impacts Wednesday in much of the Southwest and California’s Central Valley. They will hold at that level through Friday.
There are a few small pockets of Level 4 or “extreme” HeatRisk conditions predicted in the deserts of southeastern California and southern Nevada on Thursday into the start of the weekend. Las Vegas is forecast to reach Level 4 from Thursday through Saturday.
Where records could occur
The potential for record warmth will transition from spotty coverage to start the week to more widespread by Thursday.
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Much of Texas experienced record-warm low temperatures Monday, and a couple locations also set record highs from 105 to 110. More record highs are expected in Texas on Tuesday before the core of the heat shifts to the west.
Las Vegas is forecast to reach 108 on Wednesday, one degree from the June 5 record of 109. Predicted highs of 112 and 110 on Thursday and Friday would set calendar-day records. Thursday’s forecast high would also be the hottest observed there so early in the year.
Nighttime lows will also threaten records in Vegas, only dipping into the mid-80s later this week.
In the Desert Southwest, the hottest locations will easily surpass 110 degrees. Phoenix is forecast to set a record high of 113 on Thursday, while Needles in eastern California near the border of Arizona is predicted to reach 114.
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In California’s Death Valley — which is notorious for being one of the hottest places on Earth — high temperatures are likely to top 120 on several days. Forecast highs Wednesday through Saturday are 122, 125, 123 and 120. If Death Valley manages to hit 124 during this stretch, it would mark its highest temperature so early in the season.
With Las Vegas on track to record one of their earliest 110 degree days this week and Death Valley flirting with one their earliest 125 degree days, a reminder how hot these cities were last summer. #heat pic.twitter.com/LvKb19rzMP
— Kathryn Prociv (@KathrynProciv) June 4, 2024
To the north, numerous locations in the California’s Central Valley could set records by Wednesday, as highs surpass 105 degrees.
Record-challenging heat will reach Northern California by Thursday, before pushing into the Pacific Northwest briefly on Friday. There’s some indication more excessive heat may emerge by early next week.
Why this heat is dangerous
While afternoon high temperatures get the most notice, the heat wave’s persistence and a lack of relief at night will make it particularly dangerous, according to the Weather Service.
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Heat waves early in the year are also of particular concern because people are not yet acclimatized to the hot weather.
For those without access to proper shelter and air conditioning, such heat can be lethal; the punishing heat across the Southern United States in 2023 resulted in record numbers of heat-related deaths, according to the Associated Press.
Last July, Phoenix registered the hottest month on record for any city in the United States with an average temperature above 100 degrees; at least 645 heat-related deaths were recorded last summer.
Even though the heat may temporarily ease and shift, above-normal temperatures are probable in the West through at least mid-June.
This heat wave coincides with the hottest period on record for the planet; each of the past 12 months has set record highs.
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Just over the past week, India observed near-record heat that led to numerous deaths, while Iraq topped 50 degrees Celsius (122 degrees Fahrenheit) for the first time so early in the year.
Stateside, South Florida and southern Texas saw repeated episodes of record heat in May. Punta Gorda, Fla., soared to 101 degrees on May 30, southwestern Florida’s highest temperature on record so early in the year.
With high temperatures becoming more extreme, extensive and longer-lasting because of human-caused climate change, the heat building over the West is probably just a preview of even more severe conditions in the pipeline by midsummer.
