The Southwest Is Bracing for a Historic Heatwave

A thermometer in the sand with a blue sky in the background

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Parts of the Southwestern United States are suffering through a historic heatwave. Between August 4 and August 8, 2025, parts of Colorado, New Mexico, Oklahoma, and Texas, are bracing for temperatures well into the triple digits, exceeding historical norms by as much as 13°F. In cities and towns across Arizona, as well as southern California and southern Nevada, the mercury may rise as high as 116°F.

While heatwaves can be the result of natural climate cycles, high temperatures across the Southwest this week have been linked to human-caused climate change. The Climate Shift Index, or CSI, is an indicator of how climate change is impacting current conditions in any given region. The CSI is a multi-point scale ranging from -5 to 5, with higher scores indicating a greater likelihood that temperatures are being influenced by climate change. In much of the Southwest this week, the CSI will be at level 5, a maximum value indicating that temperatures are five times more likely to be the result of climate change attributable to human activities.

The heat forecasted for the Southwest this week will likely fall short of all-time record highs in the impacted states. Still, triple-digit temperatures may pose a significant public health threat, and will certainly exacerbate severe, ongoing drought conditions impacting much of the region.

Using data from the National Oceanic and Atmospheric Administration’s State Climate Extremes Committee, Climate Crisis 247 identified the hottest temperatures ever recorded in each state in the Southwest. Supplemental date and location data for each state’s record-high temperature are also from NOAA. Exactly which states are located in the Southwestern U.S. vary by source, and we included each state that is often, either partially or entirely, considered to be part of the Southwestern region. States are listed in alphabetical order.

Across the eight states on this list, record high temperatures range from 115°F to 134°F. In each of these states, all-time high temperatures were reported in either June or July.

Arizona

Highest temperature on record: 128°F
Most recent date of record-high: June 29, 1994
Location of weather station(s) that reported record heat: Lake Havasu City

California

Highest temperature on record: 134°F
Most recent date of record-high: July 10, 1913
Location of weather station(s) that reported record heat: Greenland Ranch

Colorado

Highest temperature on record: 115°F
Most recent date of record-high: July 20, 2019
Location of weather station(s) that reported record heat: John Martin Dam

Nevada

*Photo by Stin-Niels Musche on Unsplash*

Highest temperature on record: 125°F
Most recent date of record-high: June 29, 1994
Location of weather station(s) that reported record heat: Laughlin

New Mexico

Highest temperature on record: 122°F
Most recent date of record-high: June 27, 1994
Location of weather station(s) that reported record heat: Waste Isolation Pilot Plant (near Loving)

Oklahoma

Highest temperature on record: 120°F
Most recent date of record-high: July 19, 1936
Location of weather station(s) that reported record heat: Altus

Texas

Highest temperature on record: 120°F
Most recent date of record-high: June 28, 1994
Location of weather station(s) that reported record heat: Monahans

Utah

*Photo by Andrey Grinkevich on Unsplash*

Highest temperature on record: 117°F
Most recent date of record-high: July 10, 2021
Location of weather station(s) that reported record heat: St. George