How long will the record heat wave last in the western U.S.?
A western United States heat wave will continue to shatter records with days of triple-digit temperatures this week, but a shift in the jet stream could bring cooler air and relief to the region before the end of March.
AccuWeather’s Bernie Rayno warns that widespread extreme heat will expand from the Southwest to the central Plains, with temperatures 15-30 degrees above historical averages by Wednesday.
Many areas in the southwestern United States have endured day after day of heat more typical of early summer than early spring. The region will face yet another week of intense heat, but there are signs of a major change before the end of March.
"The heat wave has already lasted five to seven days and appears likely to continue through Friday," said AccuWeather Vice President of Forecasting Operations Dan DePodwin.
A Los Angeles Dodgers fan covers up from the hot sun during the second inning of a spring training baseball game against the Athletics, Saturday, Mar. 21, 2026, in Phoenix. The temperature peaked at 105 F at Phoenix Sky Harbor International Airport on Saturday afternoon. (AP Photo/Ross D. Franklin)
"Phoenix has never experienced more than five days in a row with highs of 100 degrees Fahrenheit or greater during March or April," DePodwin said. "There are a couple of days with a high near 100 forecast this week, but if temperatures surpass the upper 90s on those days, we could be looking at 10 days in a row of triple-digit heat."
Unprecedented heat for so early in the year
Many locations from California to parts of Colorado and Texas have tied or broken daily record highs for a long string of days. Some have shattered old records by several degrees. Some have set new early-season high temperature records, wiping out marks set in March and April, even though April is still a week away.
"So far, we have counted 76 individual monthly temperature records being set and hundreds of daily record highs," AccuWeather Meteorologist and Social Media Producer Jesse Ferrell said. "Multiple monthly state records have likely been set during the heat wave so far, with data still being verified by government sources."
Cities that have tied or broken daily record highs for multiple consecutive days are too numerous to mention, but some include San Francisco, Sacramento, Fresno and Palm Springs, California; Las Vegas, Reno and Ely, Nevada; Phoenix, Flagstaff and Tucson, Arizona; Salt Lake City, Ogden and Cedar City, Utah; Pocatello and Boise, Idaho; Albuquerque, Santa Fe and Las Cruces, New Mexico; El Paso, Texas; and Durango, Colorado.
"San Francisco, which sits along chilly bay waters, has never recorded five consecutive days with highs in the 80s in March," DePodwin said. "There have been six days in a row with highs in the 80s, with five of those days being records. On March 21, the high was 75, which was also a record, making it six days in a row with record highs."
Phoenix reached 105 for three consecutive days last week, Palm Springs hit 108 on March 20, and Yuma, Arizona, reached a sizzling 109 that same day.
"Nine states in the western U.S. set monthly average temperature records for the period from December through February," Ferrell said. "It is a challenge to say if that will happen again for the spring season (March through May), as there are some signs of cooler weather moving in for April."
More heat this week
Looking ahead, more record highs are expected across the interior West — from Idaho to California to Texas — this week as a new bulge in the jet stream develops and reboots the massive heat dome for several more days.
Energy demands will remain high during a time of the year when the need for heating diminishes and cooling should be low.
Hundreds more daily record highs will be broken with multiple locations in the deserts topping 100 degrees, which are typically not experienced until the end of May or June.
The heat will expand again onto the Plains and into the Mississippi Valley later this week.
Relief from the heat is coming
Starting in some areas on Friday and expanding over the weekend, the massive heat dome will begin to break down across the West. The jet stream will begin to drift farther south, and with that, some cooler air from the Pacific will be drawn inland. However, there will still be some pockets of heat over the interior West.
During next week, the heat will shift from the Rockies to the Plains and the Mississippi Valley. As this happens, progressively cooler air will settle over the western third of the nation.
For example, highs in the 100s this week will give way to highs in the 80s in Phoenix for next week. Temperatures may still be a few degrees above the historical average near 80, but that is 20 degrees below what the current heat wave is offering.
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As cooler air moves in, moisture levels will increase, providing opportunities for clouds and showers.
Looking farther ahead, AccuWeather’s Long-Range Team, led by Expert Senior Meteorologist Paul Pastelok, expects more opportunities for some rain over the interior Southwest later this spring.
"We expect some influx of subtropical moisture from the Pacific and perhaps the Gulf of California to become involved later this spring," Pastelok said. "With El Niño expected to develop quickly this summer, the North American monsoon and its moisture should be on time and then near average for most of the summer," Pastelok explained.
Increased cloud cover, showers and thunderstorms would not only help ease the serious drought building across the interior West, including the Colorado River Basin, but could also help keep extreme temperatures in check.
Conditions could then trend drier and hotter than the historical average later in the summer.
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