Western heat wave shatters March records, to expand with more extremes
Record-breaking heat across the western U.S. will intensify and expand eastward, bringing temperatures 15-30 degrees above normal, increasing health risks, accelerating high-country snowmelt and raising wildfire risks.
Cities throughout the Southwest have been breaking records day after day due to extreme heat.
Dozens of record-high temperatures, including all-time March records, have already been set in the western United States during this week's heat wave, with the heat set to intensify and expand before it starts to loosen its grip.
Temperatures will climb to levels more typical of late May and June across a broad area of the western and central U.S. through this weekend and, in some areas, into next week.
Widespread highs will reach the 80s and 90s, with multiple desert locations climbing past 100 degrees Fahrenheit. These temperatures are 15-30 degrees above the historical average for the latter half of March.
Heat-sensitive individuals may face an elevated risk of health problems due to the early-season surge in warmth. Some households may not yet have switched their climate control systems from heating to cooling, which could be especially dangerous as the record-breaking heat persists.
Some hiking trails, typically popular in early spring, have been closed due to extreme heat and the risk of dehydration.
The building heat and abundant sunshine will accelerate snowmelt in the high country and rapidly dry out vegetation at lower elevations, said AccuWeather Senior Meteorologist Tyler Roys.
"Streams and rivers will be running high, fast and ice-cold, posing dangers," Roys said. "The rapid thaw could prematurely deplete much of the snowpack, which typically provides a reliable source of water during late spring and summer. Where winds increase, the risk of wildfires will rise, while lighter winds could allow pollutants to accumulate."
The recent superbloom in Death Valley, California, and other desert regions is likely to wilt and dry up quickly amid the surging heat.
The pattern is being driven by a massive area of high pressure, forcing the jet stream well to the north. This "heat dome" creates stable air that suppresses cloud formation and rainfall. Winds are generally light beneath the core of the dome but can increase along its edges.
The heat peaked early along coastal Southern California from Tuesday to Thursday, with highs in the mid- to upper 90s. In downtown Los Angeles, temperatures reached 98 Tuesday and 95 Wednesday, both setting daily records. A strengthening marine influence into the weekend will allow highs to trend downward into the 80s.
San Francisco set daily record highs from Monday through Friday. Highs have been in the 80s the entire week. On March 20, the city broke its all-time March record high, first set in 1952, by 4 degrees, reaching 89.
Working west to east, Palm Springs, California, set a new all-time March record high of 106 Wednesday and 107 Thursday, before breaking it again with 108 Friday. Highs will trend only slightly lower, remaining in the low 100s from this weekend into early next week.
Las Vegas also set an all-time March high temperature Wednesday with a reading of 94 degrees and topped it Thursday with 95 degrees, before topping it once more Friday with 97. The city could continue to break the record Saturday as well.
Phoenix also set a March record high Wednesday with a high of 102, then surpassed it with 105 Thursday and Friday. The city is poised to push that mark to 106 or higher Saturday, with daily records forecast through at least next Tuesday. If temperatures exceed 105, it would surpass any temperature previously recorded this early in the season, even into April.
Warmth will extend to Salt Lake City, Denver and other locations across the Great Basin, the Cascades and Sierras, east to the western Rockies, eastern Washington, eastern Oregon, Nevada, Idaho, Utah, western Colorado and northern Arizona into the weekend. Temperatures will challenge daily records on multiple days. If readings top 90 in Denver, it would surpass not only the March record but also the April record high.
The heat will spread well east of the Rockies into the weekend, bringing widespread highs in the 80s and 90s and challenging daily records.
Some long-standing daily records across parts of the Plains and Mississippi Valley will be in jeopardy.
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