Record-Breaking Heat Wave Grips Western US

Experts say this one-in-500-years event is a clear marker of human-caused climate change.

Mar. 21, 2026 at 4:38am

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A record-breaking heat wave has struck the western United States, with temperatures soaring to over 112°F (44.4°C) in some desert areas near the California-Arizona border. Dozens of cities have seen new March high temperature records, alarming climate experts who say this extreme heat is virtually impossible without the influence of human-induced climate change.

Why it matters

This heat wave is a stark reminder of the accelerating impacts of climate change, with seasons shifting and extreme weather events becoming more common. The intense heat poses serious risks to public health, outdoor workers, and wildlife, underscoring the urgent need for policy action to address the climate crisis.

The details

The heat wave has toppled records across the western US, with 65 cities seeing new March highs. Death Valley reached 40°C (104°F), while San Francisco tied its historic March record at 29°C (84°F). Climate scientists say this event is so rare that it would only be expected to occur about once every 500 years in a world without human-caused global warming.

  • The heat wave struck the western US on Friday, March 21, 2026.
  • Temperatures reached over 44.4°C (112°F) in desert areas near the California-Arizona border on March 21.

The players

Friederike Otto

A professor at Imperial College London and one of the authors of the study on the heat wave.

Terry Salas

A Los Angeles resident who commented on the unusual climate conditions.

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What they’re saying

“This heat wave would be virtually impossible for the time of year in a world without human-induced climate change.”

— Friederike Otto, Professor

“This is very unusual. We're still in winter. But this is global warming. The East Coast is just tornadoes and snow, and here we are, we're sizzling.”

— Terry Salas

What’s next

Climate scientists and policymakers will likely continue to study this heat wave and its implications for the region, as well as explore ways to mitigate the impacts of climate change and prepare communities for more extreme weather events.

The takeaway

This record-breaking heat wave is a stark reminder of the accelerating impacts of climate change, underscoring the urgent need for comprehensive policy action to address the climate crisis and protect vulnerable communities and ecosystems.