Warning in Effect Now: Areas and Timeline
An Extreme Heat Warning is currently in effect across a wide stretch of Arizona, covering the following areas: Western Pima County including Ajo and Organ Pipe Cactus National Monument; the Upper Santa Cruz River and Altar Valleys including Nogales; Lake Havasu and Fort Mohave; Marble and Glen Canyons; Grand Canyon Country; Aguila Valley; Kofa; Parker Valley; the Northwest Valley; and Tonto Basin. The warning was issued on July 23, 2026, at 12:13 PM MST and runs through July 25, 2026, at 8:00 PM MST. This is an active, ongoing alert, if you are in any of these areas, protective measures are needed right now and will remain necessary through the full duration of the warning.
The warning was issued jointly by four National Weather Service offices: NWS Tucson AZ, NWS Las Vegas NV, NWS Flagstaff AZ, and NWS Phoenix AZ, a coordinated response that reflects the geographic breadth of the heat event and the seriousness with which forecasters are treating current conditions.
What the National Weather Service Is Telling You to Do Right Now
The National Weather Service is issuing clear, direct guidance for everyone in the affected areas. First and most urgently: do not leave young children or pets in unattended vehicles. According to the official alert, car interiors will reach lethal temperatures in a matter of minutes. This is not a precaution to take lightly, it applies any time you step away from a parked vehicle, even briefly.
For those who work or spend time outdoors, NWS advises taking extra precautions throughout this warning period. When possible, reschedule strenuous activities to early morning or evening, when temperatures are lower. Wear lightweight and loose-fitting clothing, and drink plenty of water. Know the signs and symptoms of heat exhaustion and heat stroke before you head outside, not after you start feeling unwell.
The alert also references guidance from the Occupational Safety and Health Administration (OSHA) for outdoor workers specifically: schedule frequent rest breaks in shaded or air-conditioned environments. Workers and supervisors should treat this as a baseline requirement, not an optional accommodation, for the duration of the warning.
If anyone around you is overcome by heat, move them immediately to a cool, shaded location. The National Weather Service is explicit: heat stroke is a medical emergency. Call 9-1-1 without delay if you suspect heat stroke. Do not wait to see if someone improves on their own.
Connecting This Alert to Broader Preparedness
Extreme heat warnings of this scale, spanning areas from the Sonoran Desert near the Mexican border all the way north to the Grand Canyon corridor, are a reminder of why heat preparedness planning matters before conditions become dangerous. At USRiskRadar, we maintain evergreen guidance on heat emergency planning, including how to identify cooling centers in your area, how to build a communication plan for vulnerable family members, and how to assess your home’s ability to stay cool during extended heat events. The measures NWS is recommending right now, hydration, shade, adjusted schedules, and vehicle safety, are the same core principles that appear in sound preparedness planning at any time of year. If this warning has caught you without a plan, use the remaining hours of July 23 to put basic steps in place for July 24 and 25, when the warning remains fully in effect.
Source: National Weather Service Tucson AZ, Las Vegas NV, Flagstaff AZ, and Phoenix AZ. Extreme Heat Warning effective July 23, 2026, 12:13 PM MST through July 25, 2026, 8:00 PM MST. Always monitor official NWS alerts at weather.gov for the most current information.
For the fundamentals that apply beyond this specific alert, see our Power Outage Preparedness guide.
Source: National Weather Service (NWS Tucson AZ, NWS Las Vegas NV, NWS Flagstaff AZ, NWS Phoenix AZ), active alert data retrieved 2026-07-23 19:39 UTC via api.weather.gov.
