The first official day of the Northern Hemisphere's spring in March 2026 felt more like summer across much of the southwestern United States. Numerous high-temperature records fell on March 20, 2026 amid a bout of extreme heat. Phoenix has never hit 100 degrees before March 26 in 137 years of record-keeping. Yuma, Arizona reached a record high of 109°F, which is 28 degrees above the 1991-2020 climatological normal for that date. Four other locations—near Yuma and Martinez Lake in Arizona and Ogilby and Winterhaven in California—tied for the highest temperatures in the U.S. that day, reaching 112°F (44°C). A new March record was set in Hermosillo, Mexico, where temperatures reached 108°F (42°C).
The heat was driven by a persistent high-pressure system, which the NWS noted was similar in strength to conditions seen in summer. The high-pressure system remained over the region for more than a week, keeping the air dry and skies clear across a vast stretch of the U.S. and Mexico. The heat was expected to spread east into the U.S. Midwest and Southeast by the following week. A heat dome is baking the Southwest and creeping eastward, potentially one of the most expansive heat waves in American history. A long-lasting weather pattern is poised to blast hot air across the eastern U.S., threatening to shatter record high temperatures in cities like New York and Washington, D.C. The weather service warned that since people are not acclimated to this level of heat this early in the year, it will be more impactful than usual.
Measurements from weather stations on March 20 pinpointed some of the highest U.S. temperatures in Arizona and California. Several other U.S. states saw temperatures soar in late March, including Texas where Lubbock experienced several days in the mid to upper 90s. Sweltering temperatures extended into Mexico as well. Temperatures could reach 107 degrees in Phoenix, Arizona, and 90-degree heat in Los Angeles in March. A spring heatwave is sweeping across the US East Coast, with temperatures forecasted to reach the mid-90s in Washington DC and North Carolina. Over 20 states are in the path of the heatwave, with temperatures 20 degrees above seasonal norms in cities like New York and Philadelphia. Parts of California and Arizona were under extreme heat warnings, with temperatures at or above 100°F in the Southwest. The Yuma Desert reached 112°F, a record for the highest March temperature in the United States.
This record-shattering heat would be 'virtually impossible' without the effects of climate change.
Extreme heat is creating 'non-survivable' conditions for humans in heatwaves, with older people particularly susceptible. Heatwaves in Phoenix (2023) and other global cities had non-survivable periods for older people, even in shade for some.
Snow surveys across the American West show record-low snowpack levels after a historically warm winter and searing March temperatures. California's Sierra Nevada had just 4.9 inches of snow water equivalent (SWE), or 18% of average, as of Monday ahead of the April 1 survey. The Colorado River headwaters had just over 4 inches of SWE, or 24% of average, less than half the previous record low. The Great Basin had 16% of average SWE, the lower Colorado region 10%, and the Rio Grande 8% as of Monday.
Americans in every state have been warned to brace for extreme weather, including deadly heat in the Southwest and a polar vortex in the Midwest and East. Two storms will dump snow by the foot over northern Great Lakes states. The polar vortex will again invade the Midwest and East with soul-crushing Arctic chill. Around the same time as the heat starts blasting Phoenix, the polar vortex is forecast to send its chill deep into the Midwest and East, even bordering some of the Southeast. Minneapolis will hover around zero (-18 C) for a low, and Chicago will be in the single digits Tuesday. The next day, temperatures in the teens and 20s in the Northeast and 20s in the Mid-Atlantic. Two storm systems in a row — one Friday, then another Sunday — will dump snow.
A marine heatwave in southern California, caused by a high-pressure system, is flashing warning signs with record-breaking water temperatures.
The Great Flood of 1862 dropped a record-setting amount of rain along the U.S. West Coast from December 1861 through January 1862. San Francisco and Sacramento, CA recorded 34 and 37 inches of rain respectively over the course of two months during the Great Flood of 1862.
A map shows air temperatures on the afternoon of March 20, modeled at 2 meters above the ground, produced with a version of the GEOS model. The darkest reds on the map indicate temperatures reaching or exceeding 104 degrees Fahrenheit (40 degrees Celsius). The NOAA-CIRES-DOE Twentieth Century Reanalysis (20CR) project has generated a four-dimensional global atmospheric dataset of weather spanning 1806 to 2015. The 20th Century Reanalysis Project is led by NOAA's Physical Sciences Laboratory (PSL) and CIRES at the University of Colorado, supported by the Department of Energy. The reanalyses assimilate only surface observations of synoptic pressure into NOAA's Global Forecast System and prescribe sea surface temperature and sea ice distribution. The most recent version of this reanalysis, V3, provides 8-times daily estimates of global tropospheric variability across 75 km grids, spanning 1836 to 2015 (with an experimental extension from 1806 to 1835). There are three previous versions of the reanalysis: V1, V2, and V2c. Version V2c covers 1851-2012 (with an experimental 2013-2014 extension).
The Southwest will soon bake with day after day of record 100-degree-plus (38 Celsius-plus) heat. Some forecasts see 98 F (almost 37 C) in Phoenix on Tuesday, followed by 103, 105 and two days of 107 (almost 42 C).
Nearly every part of the United States is getting walloped by wild weather or just about to be.
March 2024 was the most abnormally hot month in 132 years of records for the US, with an average temperature 5.19°C above the 20th-century normal.
14 states have notched their hottest March day on record since the heat dome started. It has already started in Los Angeles, with unusual 90-degree March weather. On Wednesday, Washington, D.C., residents walked around in shorts in record-breaking 86 degrees Fahrenheit (about 30 C). A heat dome will form early next week and park over the Southwest, baking temperatures to triple digits that haven’t been seen this early in the year.
The specific health impacts or fatalities resulting from the extreme heat events have not been confirmed, though research warns of 'non-survivable' conditions. How local governments and emergency services are responding to the heatwaves and other extreme weather remains unclear, with details on measures like cooling centers or public warnings not specified. The exact economic costs or damages associated with the heatwaves and low snowpack are unknown, including impacts on agriculture, energy, and infrastructure.
How long the heat dome is expected to persist, and when temperatures will return to normal, is uncertain, though forecasts indicate eastward expansion. What specific measures are being taken to protect vulnerable populations, such as the elderly, from the 'non-survivable' heat conditions has not been detailed, despite research highlighting the risks.