Millions of Americans from the Pacific coast to the Rocky Mountains have endured unseasonably warm and even dangerous temperatures this week, with readings up to 17 degrees Celsius above the March average.

The rapid attribution study found the event sits firmly outside the range of natural climate variability, making it effectively impossible in a world without greenhouse gas emissions. The finding adds to a growing body of attribution science that can now link specific weather events to climate change within days of their occurrence.

The heatwave comes amid a broader pattern of extreme weather events across the United States, with Nebraska still recovering from wildfires that consumed nearly 800,000 acres in the largest blaze in the state's history.