The dangerous heatwave shattering temperature records for March throughout the southwestern United States is more than just another extreme weather event. It is the latest example of an unprecedented climate disruption that is occurring more frequently as the planet warms.
Experts believe that extreme, unprecedented, and deadly weather events occurring during abnormal periods and in unusual locations are increasingly putting people at risk. The Southwest is used to facing deadly heat, but not months ahead of schedule, like the 43.3°C recorded in the Arizona desert on March 19, which broke the all-time heat record for March in the United States.
On Thursday, stations in Arizona and Southern California posted preliminary values of 43°C, which would make it the hottest March day ever recorded in the United States.
“This is what real-time climate change looks like: extremes pushing the boundaries we thought were possible,” explains Andrew Weaver, a climatologist at the University of Victoria. “What was once unprecedented events are becoming recurring features of a warming world.”
“Practically impossible without climate change”
The heat observed in March would have been practically impossible without human-caused climate change, according to a report published on March 20, by World Weather Attribution, an international group of scientists studying the causes of extreme weather events.
More than a dozen scientists, meteorologists, and disaster experts interviewed by the Associated Press classify the March heatwave into a category of ultra-extreme events, alongside the 2021 heatwave in the Pacific Northwest, the 2022 floods in Pakistan, and the deadly hurricanes Helene, Harvey, and Sandy.
The area of the United States affected by extreme weather events over the past five years has doubled compared to twenty years ago, according to the Climate Extremes Index of the National Oceanic and Atmospheric Administration (NOAA).
Today, the United States breaks 77% more heat records than in the 1970s and 19% more than in the 2010s, based on data analyzed by the Associated Press.
Extremes accelerating faster than we are
“It’s becoming really difficult to keep up with how extreme our extremes are becoming,” observes Bernadette Woods Placky, chief meteorologist at Climate Central. “This changes our level of risk, alters our relationship with weather, exposes more people to dangerous situations, in times of the year we’re not used to. Yes, we’re pushing extremes to new levels, for all types of weather.”
For public officials responsible for disaster management, this has become a major problem.
Craig Fugate, who led the Federal Emergency Management Agency (FEMA) until 2017, has noted this increase in extremes.
“Increasingly, we were operating outside the historical scenario. Flood maps, coastal inundation models, heat records: events were constantly occurring outside the range we had built our systems on. That’s simply what we were observing,” Fugate explains via email.
He adds, “We built our communities based on about a hundred years of past weather, assuming that was a good guide for the future. That assumption is shattering. And the clearest signal is not the scientific debate, it’s the insurance companies pulling out.”
Fossil fuels driving temperatures to unprecedented levels
Climate scientists at World Weather Attribution quickly analyzed to determine how much human-caused climate change played a role in this heatwave in the Southwest. They conclude that “events as hot as in March 2026 would have been practically impossible without human-induced warming.”
According to the report, this warming from burning coal, oil, and natural gas added between 2.6 and 4°C to the felt temperatures.
“What we can say with great confidence is that human-caused warming has increased the temperatures we observe under this dome of heat, and it is pushing these temperatures from just very uncomfortable levels to potentially dangerous levels,” explains Clair Barnes, a climate attribution specialist at Imperial College London and report co-author.
Examples of extreme heat and climate chaos are multiplying
The heatwave in the Southwest clearly falls into the category of “giant events,” with temperatures up to 16.7°C above normal, estimates Chris Field, a climatologist at Stanford University.
He cites five other extreme events over the past six years: a heatwave in Siberia in 2020; the 2021 heatwave in the Pacific Northwest, which made British Columbia hotter than Death Valley; the 2022 summer in North America, China, and Europe; a heatwave in 2023 in the western Mediterranean; and a heatwave in South Asia in 2023 marked by high humidity.
This does not include the heatwave that hit eastern Antarctica in 2022, with temperatures 45°C above normal. It was the largest anomaly ever observed, according to weather historian Chris Burt, author of Extreme Weather.
Weather disruptions worsened by climate change are not limited to days of extreme heat: they also include deadly hurricanes, droughts, and torrential rains, scientists at the AP have pointed out.
Devastating floods hit West Africa in 2022 and again in 2024. Iran is facing a six-year drought. And the deadly typhoon Haiyan that hit the Philippines in 2013 shocked the world.
The Superstorm Sandy in 2012 flooded New York and neighboring states, accompanied by tropical storm-force winds covering an area representing about one-fifth of the area of the continental United States. It generated seas of 3.5 meters over 3.6 million square kilometers, roughly half the size of the U.S., with energy equivalent to five Hiroshima-sized atomic bombs, details meteorologist Jeff Masters of Yale Climate Connections.
Not to be forgotten are forest fires, exacerbated by heat and drought. Among recent extremes are the Palisades and Eaton fires in 2025, which were the costliest weather disaster in the United States last year, notes Adam Smith, a meteorologist and economist at Climate Central.
“If we are seeing more extreme, more intense events, and so many records broken, it’s because of climate change,” says Friederike Otto, a climatologist at Imperial College London, who coordinates World Weather Attribution.
