The weather heat wave forecast covers a strong, slow-moving high-pressure system over the Desert Southwest that cleared skies and heated the air beneath it, forecasters said.
Scientists described the event as without precedent for March, with Nevada state climatologist Baker Perry calling it "uncharted territory" and Colorado state climatologist Russ Schumacher saying there is "no analog in March."
Dozens of daily temperature records and more than 60 all-time monthly records were already set as temperatures ran 20 to 30 degrees above normal in many locations, according to reporting on the event.
Cities beneath the high-pressure center saw extraordinary readings, with Phoenix and Albuquerque matching or exceeding their highest-ever April temperatures, and Flagstaff reaching 84 degrees in a March reading that surpassed its April record of 80 degrees.
South Lake Tahoe recorded a high of 76 degrees, beating its previous March record and matching April highs, while San Jose faced a forecast high that would break its March record, local forecasters said.
Impacts Risks And Attribution
Climatologists warned of rapid snowpack loss and a "flash drought" or "mass evaporation event," with Oregon state climatologist Larry O'Neill saying the heat was chewing through depleted snowpack and drying the landscape.
Forecasters issued early elevated fire weather warnings, with the weather service flagging elevated fire danger in east-central Oregon as the earliest such warning since 2014, officials reported.
Experts linked the extreme March warmth to broader climate trends, with Michael Mann saying the high pressure and record temperatures align with expectations for a warming planet.
A rapid-attribution study by World Weather Attribution found that human-caused climate change made the Western US heat wave about four times more likely over the past decade, and Ben Clarke said such March temperatures would be virtually impossible in a world without human-caused climate change.
Observers compared the anomaly to the June 2021 Pacific Northwest heat dome, noting that the 2021 event broke records across hundreds of stations, with Christopher Burt calling it "probably one of the greatest anomalous weather events in world history."
Officials advised people to limit outdoor activities as heat advisories and even extreme heat watches covered wide areas, while gardeners and residents adjusted routines to protect plants and health during the prolonged early-season heat.
