An Extreme Heat Warning is currently in effect across a large portion of Arizona, covering communities from the northwestern valleys to the southern borderlands. The warning was issued by multiple National Weather Service offices, including NWS Phoenix AZ, NWS Las Vegas NV, NWS Tucson AZ, and NWS Flagstaff AZ, and runs from 2:30 PM MST on July 25, 2026 through 8:00 PM MST on July 27, 2026.
The areas under this warning are broad and include: the Northwest Valley; Parker Valley; Aguila Valley; Tonto Basin; Lake Havasu and Fort Mohave; Western Pima County including Ajo and Organ Pipe Cactus National Monument; Upper Santa Cruz River and Altar Valleys including Nogales; Yavapai County Valleys and Basins; Marble and Glen Canyons; and Grand Canyon Country. If you live in or are traveling through any of these zones, this warning applies to you right now.
What the National Weather Service Is Telling You to Do
According to the National Weather Service, an Extreme Heat Warning means that a period of very hot temperatures, even by local standards, is occurring. That distinction matters in Arizona, where residents are accustomed to summer heat. When NWS characterizes conditions as extreme by local standards, it signals conditions that go beyond what area residents typically manage through routine precautions.
NWS is directing anyone who works or spends time outdoors to take extra precautions immediately. Where possible, strenuous activities should be rescheduled to early morning or evening hours, when temperatures are lower. If outdoor work cannot be avoided, the alert specifically references guidance from the Occupational Safety and Health Administration (OSHA), recommending frequent rest breaks in shaded or air-conditioned environments.
The alert emphasizes wearing lightweight and loose-fitting clothing and drinking plenty of water. Residents and workers should also make sure they know the signs and symptoms of both heat exhaustion and heat stroke before going outside.
Heat stroke is a medical emergency. If anyone is overcome by heat, NWS instructs that the person should be moved immediately to a cool, shaded location, and that 911 should be called without delay. Do not wait to see if symptoms resolve on their own.
Public cooling shelters are available in some areas covered by this warning. The NWS advises consulting your county officials directly for information on shelter locations near you.
Connecting This Alert to Your Preparedness Plan
Extreme heat is consistently one of the deadliest weather-related hazards in the United States, and the communities covered by this warning, many of them rural, remote, or at high elevation, face specific challenges around access to cooling resources and emergency services. At USRiskRadar, we regularly cover heat preparedness as a core part of disaster readiness: knowing your nearest cooling center, keeping an emergency water supply on hand, and having a communication plan for checking on elderly or isolated neighbors are steps that apply directly during an event like this one. The window between feeling overheated and experiencing a heat-related emergency can be short, particularly during a warning-level event, which is precisely why NWS urges action now, while conditions are still manageable for those who prepare.
This article is based on an active alert issued by the National Weather Service. Monitor NWS Phoenix AZ and your local NWS office for updates as conditions evolve through July 27, 2026.
For the fundamentals that apply beyond this specific alert, see our Power Outage Preparedness guide.
Source: National Weather Service (NWS Phoenix AZ, NWS Las Vegas NV, NWS Tucson AZ, NWS Flagstaff AZ), active alert data retrieved 2026-07-25 22:00 UTC via api.weather.gov.
