Why is there a heatwave in the southwestern USA?
A large heat dome has developed over the southwestern United States as a strong upper-level ridge of high pressure traps hot air near the surface. This stagnant weather pattern allows temperatures to build over several consecutive days while limiting cloud cover and rainfall (1).
Forecasts indicate that two separate heat domes are expected to merge into one larger system over the eastern United States, expanding the area experiencing dangerous heat and humidity during the coming week (2).
Which cities or areas are affected by the heatwave?
The heatwave is currently affecting much of the southwestern United States. The areas experiencing the most dangerous heat include:
- Arizona: Phoenix, Tucson, Yuma, Southeast Pinal County, Upper Gila River Valley, and Upper San Pedro River Valley
- New Mexico: Las Cruces and the Mesilla Valley
- Texas: El Paso, western Texas, and Palo Duro Canyon State Park
Over the coming days, the heat dome is forecast to expand into parts of the central and eastern United States, including the Great Plains, Midwest, Southeast, and East Coast (3).
How long will the heatwave last?
The current heatwave continues across portions of the Southwest, with Extreme Heat Warnings and Heat Advisories remaining in effect through June 25.
Dangerous heat is expected to persist through the upcoming weekend, with some areas remaining unusually hot into next week before conditions begin to ease (4).
Are there any alerts in place?
Multiple heat-related alerts remain in effect across the affected regions. Extreme Heat Warnings remain in effect until the evening of June 25 for parts of Arizona, including the Phoenix metropolitan area, Tucson Metro Area, Yuma, the Lower Colorado River Valley, Southeast Pinal County, Upper Gila River Valley, and Upper San Pedro River Valley, where temperatures are expected to reach 106°F to 113°F.
Heat Advisories also remain in effect through June 25 for portions of southern New Mexico, El Paso, western Texas, Palo Duro Canyon, and parts of the Seattle metropolitan area.
In Arizona, Maricopa County residents can access free cooling centers, transportation assistance, and drinking water by calling 2-1-1. Public cooling shelters are also available in some communities.
Residents should continue monitoring local emergency management agencies for updated heat alerts and safety information, particularly if hot, dry conditions increase the risk of new or worsening wildfires (5).
