Why is there a heatwave in the U.S. Southwest?

On June 5, 2024, the U.S. National Weather Service issued excessive heat warnings and heat advisories for much of California, Arizona, Nevada, and southern Texas (1).

An expansive high-pressure system, or "heat dome," is the primary driver behind the scorching temperatures experienced across U.S. Southwest. This atmospheric phenomenon, characterized by sinking air and clear skies, creates a dome-like structure that traps heat near the Earth's surface.

The lingering high-pressure system over Mexico and Central America has worsened the situation, intensifying the heatwave.

This region typically experiences hot and dry conditions during the summer months, but the combination of the heat dome and underlying climatic patterns has led to exceptionally high temperatures. Human-caused climate change is a contributing factor in the increased length and intensity of heatwaves.

Which cities or areas are affected by the heatwave?

The heatwave is expected to significantly impact desert communities, California’s Central Valley, and South Texas.

These cities will be or are currently being impacted by the heatwave:

• Abilene, Texas
• Albuquerque, New Mexico
• Austin, Texas
• Bakersfield, California
• El Paso, Texas
• Fresno, California
• Houston, Texas
• Las Vegas, Nevada
• Phoenix, Arizona
• Sacramento, California
• San Angelo, Texas
• San Antonio, Texas
• Tucson, Arizona
• Victorville, California

How long will the heatwave last?

The heatwave commenced building from Tuesday into Wednesday and is expected to persist throughout the week.

While the exact duration varies by location, forecasts indicate that the extreme heat conditions will continue for several days.

In some areas like South Texas, the heatwave may gradually ease towards the end of the week, but residents should remain vigilant and prepared for prolonged heat exposure.

Are there any alerts in place?

Excessive heat warnings and watches have been issued for various regions, including parts of California, Arizona, Nevada, and Texas. These alerts urge residents to take necessary precautions to prevent heat-related illnesses and dehydration, emphasizing the importance of staying hydrated, seeking shade, and avoiding strenuous outdoor activities during peak heat hours.

Trails and recreational areas in Phoenix, Arizona, such as Camelback Mountain, have been temporarily closed from Wednesday through Friday. This closure aims to prevent heat-related emergencies and underscores the seriousness of the heatwave's impact on outdoor activities (2).