Record-Breaking March Heatwave Raises Concerns Across the Southwest
As March unfolds, an unprecedented heatwave is sweeping across the Southwestern United States, shattering temperature records in California, Arizona, Nevada, and Utah. While some cities are experiencing heat levels typical of late April, climatologists are expressing astonishment at the scale of this weather anomaly.
Baker Perry, Nevada’s state climatologist, noted the extraordinary nature of the situation, stating, “It’s uncharted territory.” Russ Schumacher, Colorado’s state climatologist, echoed this sentiment, remarking, “There’s no analog in March, not even close.”
The cause of this intense heat is a strong, slow-moving high-pressure system over the Desert Southwest. This system, intensified by a kona storm and its associated atmospheric river, is leading to clear skies and heating the air below. As a result, dozens of cities have already broken March temperature records by significant margins.
Four cities, including Phoenix and Albuquerque, have not only set new March records but have also matched or exceeded their highest temperatures ever recorded in April. This pattern of record-breaking temperatures is not just limited to monthly records but also includes daily highs. South Lake Tahoe’s temperature reached 76 degrees, breaking its previous March record by 5 degrees and matching April’s highest-ever reading.
Perry highlighted the unusual nature of these events, explaining, “It’s not out of the ordinary, especially in our climate that we have now, to break daily records, but monthly records are a little harder. Typically, they’re not shattered.”
San Jose is also experiencing the heat, with a forecast high of 90 degrees expected to break a monthly record by a degree. Meanwhile, Arizona remains a focal point of the heatwave, with Flagstaff reaching 84 degrees, demolishing its previous March record of 73 degrees and surpassing its April record of 80 degrees.
In Phoenix, temperatures reached 105 degrees on Thursday, with forecasts predicting 107 degrees on Friday. Such temperatures are usually not seen until early June, with the earliest occurrence being May 2, 1947.
Arizona’s state climatologist, Erinanne Saffell, emphasized the potential for similar events in the future: “The way I look at these things is, once they happen, they can happen again.”
Climatologists are struggling to find a historical precedent for this event. While the modern era of routine weather balloon measurements dates back to the 1940s, no March heatwave compares to the current situation. Earlier significant March heatwaves, such as those in 1907 and 1910, appear less intense in comparison.
The closest parallel is the June 2021 heat dome that shattered records across the Pacific Northwest and British Columbia. Weather historian Christopher Burt described it as “probably one of the greatest anomalous weather events in world history, not just U.S. history.”
During the June 2021 heatwave, temperatures were 20 to 35 degrees above normal, breaking daily and monthly records. Similarly, the current heatwave has set hundreds of daily records and over 60 all-time monthly records, with temperatures 20 to 30 degrees above normal.
Schumacher draws a comparison to the 2021 anomaly, noting that this heat dome struck a region accustomed to extreme summer heat, albeit earlier than expected. Daniel Swain, a climate scientist at UC Agriculture and Natural Resources, commented, “Typically, we don’t consider summer weather to be normal in winter,” during a YouTube livestream.
Concerns are rising about the aftermath of this high heat and low humidity period. Oregon state climatologist Larry O’Neill described it as a “flash drought” or “mass evaporation event,” rapidly depleting snowpacks and drying landscapes.
O’Neill warned, “These early season heat waves are real killers for our drought status and for our water supply. I don’t want to say we’re in full freakout mode, but there’s a very clear-eyed picture of what we face this summer.”
With the weather service warning of elevated fire danger in east-central Oregon, the earliest such warning since 2014, O’Neill predicts heightened fire risks across the region this summer. “Wildfire smoke knows no boundaries,” he noted.
While this anomalous high-pressure system and its associated temperatures are unprecedented, climate change experts were not surprised. Michael Mann, a climate scientist at the University of Pennsylvania, emphasized, “The high surface pressure and record temperatures in Southwestern U.S. are consistent with our expectations on a warming planet.”
A rapid-attribution study by World Weather Attribution found that climate change has made such heatwaves about four times more likely in the past decade alone. Ben Clarke, a research associate at Imperial College London, stated, “These temperatures are completely off the scale for March, and our data shows that they would be virtually impossible in a world without human-caused climate change.”
Original Story at www.sfchronicle.com