The Digester

Historic March heatwave shatters records across US West

Mar 20th 2026

A late winter heatwave pushed temperatures far above normal across the US southwest, breaking multiple records and prompting heat warnings, park closures and safety alerts as conditions are expected to peak through the weekend.

  • Temperatures 25 to 35 degrees above normal have led to multiple daily and monthly records across California, Nevada and Arizona.
  • North Shore, California tied the highest March temperature in US history at 108F (42.2C).
  • Palm Springs area and Cathedral City reached about 108F, and Thermal is forecast to hit 110F (43.3C).
  • Phoenix set a record overnight low of 69F (20.5C) on March 19 and reached triple digits by midday, the earliest 100F readings in almost 40 years.
  • Heat warnings remain in effect through Sunday with a peak expected Friday, and cooling is forecast for next week.
  • National parks and recreation areas issued closures and safety alerts, including Lake Mead trail closures and an extreme heat advisory for Grand Canyon.

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