An Extreme Heat Warning is in effect right now across six Arizona areas: the Northwest Valley, Aguila Valley, Parker Valley, Northwest Plateau, Marble and Glen Canyons, and Grand Canyon Country. The warning, issued by the National Weather Service Phoenix AZ, coordinated with NWS Las Vegas NV and NWS Flagstaff AZ, runs from August 4, 2026, through August 7, 2026, at 8:00 PM MST. If you live, work, or are traveling through any of these zones during that window, this warning applies to you.
The National Weather Service describes an Extreme Heat Warning as a period of very hot temperatures that will be extreme even by local standards, meaning conditions that exceed what residents of these already-hot regions are used to managing. That framing matters. This is not a routine summer heat advisory.
h2>What NWS Is Telling You to Do Right Now
The guidance from the National Weather Service is direct and action-oriented. Here is what it says, broken down by who is most at risk.
If you work or spend time outdoors: Reschedule strenuous activities to early morning or evening whenever possible. Wear lightweight, loose-fitting clothing and drink plenty of water throughout the day. The Occupational Safety and Health Administration, cited directly in the NWS alert, recommends scheduling frequent rest breaks in shaded or air-conditioned environments for anyone doing outdoor work. Do not push through discomfort.
Know the difference between heat exhaustion and heat stroke. Heat exhaustion is serious. Heat stroke is a medical emergency. If someone around you is overcome by the heat, move them to a cool, shaded location immediately. If heat stroke is suspected, call 911 without delay. The NWS alert is explicit on this point: heat stroke requires emergency response, not a wait-and-see approach.
Cooling shelters are available. Public cooling shelters are open in some areas covered by this warning. Contact your county officials directly for locations and hours. This resource exists specifically for people who do not have reliable air conditioning at home or who need a safe place to wait out the hottest hours of the day.
These are not suggestions layered on top of the official alert. They are the official alert. The National Weather Service included each of these points in the warning text itself because they represent the actions most likely to prevent a heat-related death or hospitalization during this event.
Connecting This Warning to Your Broader Preparedness Plan
Extreme heat is consistently one of the deadliest weather hazards in the United States, and the Southwest faces it with regularity. That familiarity can breed complacency, which is exactly what makes a warning like this one worth taking seriously even for long-time Arizona residents. A solid preparedness baseline for heat events includes knowing in advance where your nearest cooling shelter is, keeping water accessible at home and in your vehicle, and having a check-in plan for elderly neighbors, children, or anyone in your household who may not recognize the symptoms of heat illness in themselves. The NWS alert covering the Northwest Valley, Aguila Valley, Parker Valley, Northwest Plateau, Marble and Glen Canyons, and Grand Canyon Country through August 7 is a good prompt to confirm those basics are in place before the hottest hours arrive.
Source: National Weather Service Phoenix AZ, Las Vegas NV, and Flagstaff AZ. Extreme Heat Warning effective August 4, 2026, 12:56 PM MST through August 7, 2026, 8:00 PM MST.
For the fundamentals that apply beyond this specific alert, see our Extreme Heat Preparedness guide.
Source: National Weather Service (NWS Phoenix AZ, NWS Las Vegas NV, NWS Flagstaff AZ). Active alert data retrieved 2026-08-04 22:01 UTC via api.weather.gov.
