Climate Shift Index AlertJune 11, 2024

Climate change influencing severe heat in Southwest U.S.

The Southwest United States is poised to experience unusually intense heat over the next several days (June 11-13), with high temperatures made at least 5 times more likely because of human-caused climate change. 

Note: This event may continue beyond June 13. Use the Global Climate Shift Index map to stay updated on heat in your region.

CSI Alert Southwest (June 11) EN

How unusual is this heat event?

  • This week, millions of people across the U.S. Southwest will be exposed to multiple days moderate to major heat, which will significantly affect those without access to effective cooling and/or adequate hydration.

  • Excessive Heat Warnings and Watches have been issued for parts of Arizona, New Mexico, and Nevada including Phoenix, Tucson, Las Cruces and Las Vegas.

  • High temperatures of 105°F to 112°F are expected in the lower deserts, and 102°F to 108°F in the higher terrain, through June 13. 

  • Elevated nighttime temperatures in the 73°F to 83°F range are expected across much of this region.

Note: Find information on cooling centers, hydration stations and respite centers in the Phoenix area (Maricopa County) and the Las Vegas area (Clark County).

This is a continuation of an extreme heat event that started last week.

  • Last week, climate-fueled extreme heat impacted the Southwest with record-setting high temperatures recorded in Phoenix (113°F), Las Vegas (111°F), Reno (98°F), and Flagstaff (91°F) on June 6 (the peak of the heat wave).

  • Record warm low temperatures were also set in Phoenix (87°F) and Las Vegas (85°F). Unusually high lows contribute to the risk of heat related illness, by not allowing time for our bodies to cool down.

How has climate change influenced this heat?

  • Daily average temperatures are expected to reach Climate Shift Index (CSI) levels of 5 in central and eastern California, Nevada, New Mexico, Utah, Colorado, and Arizona. A CSI level 5 indicates that human-caused climate change made this excessive heat at least five times more likely, signifying an exceptional climate change event. 

  • Over the next three days, 17 million people in the Southwest will experience at least one day with CSI level 5.

Use the Climate Shift Index global map to see CSI levels in your city and region, and see our FAQs to learn about the CSI in both English and Spanish. 

What impacts are we seeing with this continued extreme heat?

What do experts say?

Dr. Andrew Pershing, VP of Science at Climate Central, said: 
“The Southwest is the hottest part of the country, and human-caused climate change is making it even hotter. Heat waves like this will continue to become longer, more intense, and more dangerous until carbon pollution ends.”

How do we know climate change is influencing this heat?

The Climate Shift Index uses peer-reviewed methodology to estimate how climate change has increased the likelihood of a particular daily temperature. It can be run using historical or forecast temperatures.

Using computer models, we compared the likelihood that these temperatures would occur in a world without carbon emissions released by humans, versus in today's world with decades of carbon emissions building up in the atmosphere. This is an established scientific method to determine how much climate change has or has not affected individual extreme weather events.

For this analysis, temperatures come from the National Center for Environmental Prediction’s Global Forecast System.

To request an interview with a Climate Central scientist, please contact Peter Girard at

Reporting resources

Until greenhouse gas emissions end, heatwaves everywhere will continue to become hotter and more dangerous. Explore quick facts and local analyses on the links between climate change and extreme heat in: