In March 2026, the first official day of the Northern Hemisphere’s spring felt more like summer across much of the southwestern United States, according to official sources. Numerous high-temperature records fell on March 20, 2026, amid a bout of extreme heat, with Yuma, Arizona, reaching a record high of 109°F, which is 28 degrees above the 1991-2020 climatological normal for that date, the National Weather Service reported. Temperatures at or above 100 degrees Fahrenheit were forecast in the Southwest, with Yuma Desert reaching 112°F on Friday, a record for the highest March temperature in the U.S., according to the National Weather Service. Phoenix has never hit 100 degrees before March 26 in 137 years of record-keeping, the NWS stated, while at least 479 weather stations broke March temperature records from Wednesday through Saturday, according to the National Center for Environmental Information. Fourteen states have set their hottest March day on record during this heat dome, including California, Arizona, Nevada, Kansas, New Mexico, Nebraska, Utah, South Dakota, Missouri, Iowa, Colorado, Wyoming, Minnesota, and Idaho, according to climatologist Maximiliano Herrera, though other reports focus on city records in fewer states, leaving uncertainty about the exact geographic scale of state-wide records.
A map shows air temperatures on the afternoon of March 20, 2026, modeled at 2 meters above the ground, produced with a version of the GEOS model, according to official sources. The darkest reds on the map indicate temperatures reaching or exceeding 104 degrees Fahrenheit (40 degrees Celsius), official sources said. Measurements from weather stations on March 20, 2026, pinpointed some of the highest U.S. temperatures in Arizona and California, according to official sources. The heat was driven by a persistent high-pressure system, which the NWS noted was similar in strength to conditions seen in summer, and it 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, official sources reported. Several other U.S. states saw temperatures soar in late March 2026, with Lubbock, Texas, experiencing several days in the mid to upper 90s, and sweltering temperatures extended into Mexico in late March 2026, according to official sources. A new March record was set in Hermosillo, Mexico, where temperatures reached 108°F (42°C), news reports indicated. The heat was expected to spread east into the U.S. Midwest and Southeast by the following week, official sources said, with a gigantic heat dome baking the Southwest and creeping eastward, potentially one of the most expansive heat waves in American history, according to meteorologists and weather historians. A heat dome is expanding east, threatening 23 states with temperatures up to 30 degrees above normal for late-March, meteorologists reported, though other sources describe it covering one-quarter to one-third of the continental U.S. without a total state count, creating disagreement over how many states are directly affected. Parts of Oklahoma, Nebraska, northern Texas, and South Dakota are registering highs at least 20 degrees Fahrenheit above their March averages, multiple reports indicate.
Temperatures could reach 107 degrees in Phoenix, Arizona, and 100 degrees in Los Angeles during the March heatwave, multiple reports indicate. Some forecasts see 98°F in Phoenix on Tuesday, followed by 103, 105 and two days of 107°F, according to research sources. It has already started in Los Angeles, with unusual 90-degree March weather that had people in shorts and tank tops seeking shade wherever they could find it, research sources said.
This record-shattering heat would be 'virtually impossible' without climate change, according to World Weather Attribution. March 2024 was the hottest March on record for the U.S., with an average temperature 9.35°F above the 20th century normal, the most abnormally hot month in 132 years of records, NOAA data shows.
Southern California coastal waters have recorded record-breaking high temperatures, with La Jolla station registering 10°F above historical average last month, multiple reports indicate. The marine heatwave is caused by a high-pressure atmospheric system, not El Niño, and could evolve into something similar to 'the Blob' if it persists, scientists said. March 2024 was the second warmest month ever measured in the ocean, with an average sea temperature of nearly 21 degrees Celsius, Copernicus data reported.
Snow surveys across the American West show record-low snowpack levels after a historically warm winter and searing March temperatures, multiple reports indicate. Snow water equivalent (SWE) measurements are exceptionally low, with California's Sierra Nevada at 18% of average and Colorado River headwaters at 24% of average as of early April, according to the state's department of water resources. The Great Basin had 16% of average SWE, the lower Colorado region 10%, and the Rio Grande 8% as of early April, data from a branch of the USDA shows.
Extreme heat has created 'non-survivable' conditions in past heatwaves for older people, even without reaching the theoretical wet bulb temperature limit of 35°C, according to new research. Heatwaves in Mecca (2024), Bangkok (2024), Phoenix (2023), Mount Isa (2019), Larkana (2015), and Seville (2003) had non-survivable periods for older people exposed to full sun, the research stated.
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, multiple reports indicate. The Southwest will soon bake with day after day of record 100-degree-plus heat, research sources said. Two storms will dump snow by the foot over northern Great Lakes states, and the dreaded polar vortex will again invade the Midwest and East with soul-crushing Arctic chill, research sources reported. Weather whiplash has already hit much of the East, with Washington, D.C., residents walking around in shorts in record-breaking 86 degrees Fahrenheit on Wednesday, research sources said. 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, according to Ryan Maue. Minneapolis will hover around zero for a low, and Chicago will be in the single digits Tuesday, Ryan Maue said. The next day, temperatures in the teens and 20s in the Northeast and 20s in the Mid-Atlantic, and even Atlanta could drop to the 20s, research sources indicated. Two storm systems in a row — one Friday, then another Sunday — will dump snow, research sources reported.
El Niño may be returning, which could lead to higher global temperatures and more extreme weather, scientists said.
How long the high-pressure system is expected to persist, and when temperatures will return to normal, remains uncertain. What specific health impacts or fatalities have resulted from the March 2026 heatwave in the U.S. and Mexico is not yet confirmed. The projected economic costs or damages from these extreme weather events, and any official emergency measures beyond general warnings, are unknown. The current status of water supply shortages due to low snowpack and any mitigation plans in effect remain unknown.