Record March Heat Scorches Western U.S.

Dozens of cities shatter temperature records as climate change drives extreme weather events.

Mar. 23, 2026 at 8:15am

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A record-breaking heat wave swept across the western United States this week, shattering March temperature records in dozens of cities. The highest reading reported was 43.3 degrees Celsius near Martinez Lake, Arizona, surpassing the previous U.S. March record. Experts say the event "would have been virtually impossible without human-induced climate change" and warn that April 1 snowpack levels could fall to record lows, threatening summer water supplies.

Why it matters

This extreme heat event highlights the growing threat of climate change, with scientists attributing the record-breaking temperatures directly to human-caused global warming. The impacts could be far-reaching, from stressing power grids and water supplies to increasing the risk of wildfires in the region.

The details

Over 550 daily high-temperature records were set across the western U.S. since March 11, with at least 65 locations logging all-time March highs. In Phoenix, Arizona, temperatures matched the city's all-time April record - in March. The World Weather Attribution group said the event "would have been virtually impossible without human-induced climate change," estimating fossil fuels added 2.6-4 degrees Celsius to observed temperatures.

  • The heat wave swept across the western U.S. this week, starting on March 11.
  • On Thursday, March 21, temperatures reached 43.3 degrees Celsius near Martinez Lake, Arizona, setting a new U.S. March record.

The players

World Weather Attribution

A group of climate scientists who conducted a rapid, non-peer-reviewed analysis of the heat wave, concluding that it "would have been virtually impossible without human-induced climate change."

Friederike Otto

A climate science professor at Imperial College London and co-author of the World Weather Attribution analysis, who said the findings "leave no room for doubt" that climate change is driving weather extremes.

Daniel Swain

A climate scientist with the University of California Agriculture and Natural Resources, who linked the extreme heat and recent wildfires to climate change and warned of potential record-low April 1 snowpack levels.

Russ Schumacher

Colorado's state climatologist and a professor at Colorado State University, who said there is "no analog in March - not even close" for the level of heat observed.

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What they’re saying

“These findings leave no room for doubt. Climate change is pushing weather into extremes that would have been unthinkable in a pre-industrial world.”

— Friederike Otto, Climate science professor

“These extreme events are a stark reminder that we must act urgently to address the root causes of climate change and build resilience in our communities.”

— Daniel Swain, Climate scientist

What’s next

Experts warn that the record-low April 1 snowpack levels across western watersheds could threaten summer water supplies, underscoring the need for immediate action to address the impacts of climate change.

The takeaway

This heat wave is a clear sign that climate change is already having severe impacts on the western United States, with scientists warning that such extreme events will only become more frequent and intense unless significant steps are taken to reduce greenhouse gas emissions and build climate resilience.