Arizona Extreme Heat Warning Through August 23: How to Protect Yourself and When to Call 911

An Extreme Heat Warning is in effect right now across several communities in Arizona. The warning, issued August 20, 2026, at 11:44 a.m. MST, runs through August 23, 2026, at 8:00 p.m. MST. The areas under the warning include Aguila Valley, Parker Valley, San Carlos, the Northwest Valley, Western Pima County including Ajo and Organ Pipe Cactus National Monument, Lake Havasu and Fort Mohave, and Grand Canyon Country. The alert was issued jointly by the National Weather Service offices in Phoenix, AZ, Tucson, AZ, Las Vegas, NV, and Flagstaff, AZ.

According to the National Weather Service, an Extreme Heat Warning means a period of very hot temperatures, even by local standards, is occurring. This is not a routine heat advisory. Temperatures are expected to be severe enough that residents and workers are urged to take action now, not just avoid discomfort but reduce real physical risk.

What NWS Is Telling Residents to Do Right Now

The National Weather Service Phoenix AZ office is directing anyone who works or spends time outdoors to take extra precautions immediately. Where possible, strenuous activity should be rescheduled to early morning or evening hours, when temperatures are lower. If you must be outside during peak heat, wear lightweight and loose-fitting clothing, and drink plenty of water consistently, not just when you feel thirsty.

For those working outdoors, the alert specifically references guidance from the Occupational Safety and Health Administration, which recommends frequent rest breaks in shaded or air-conditioned environments. If a coworker or anyone nearby becomes overcome by heat, move them immediately to a cool, shaded location. Do not wait to see if they recover on their own.

Heat stroke is a medical emergency. The NWS alert is explicit on this point: call 911. Knowing the difference between heat exhaustion and heat stroke matters here. Heat exhaustion can include heavy sweating, weakness, and nausea. Heat stroke, which is life-threatening, involves a high body temperature, often above 103 degrees Fahrenheit, and can involve confusion, loss of consciousness, or hot and dry skin. If someone is showing signs of heat stroke, do not attempt to manage it at home. Call 911 immediately.

Public cooling shelters are available in some areas covered by this warning. The National Weather Service advises contacting county officials for specific shelter locations near you. If you do not have reliable air conditioning at home, or if your power is interrupted during this warning period, locating the nearest cooling shelter before you need one is a practical step to take now.

Why This Warning Fits a Larger Pattern Arizona Residents Should Know

Arizona’s desert communities are no strangers to extreme heat, but warnings at this level, covering a wide geographic spread from the Grand Canyon Country to the western Sonoran Desert, reflect conditions that push past what residents and infrastructure routinely handle. For those using this site to build longer-term preparedness, extreme heat events are among the most consistently dangerous natural hazards in the Southwest. A reliable supply of water, a plan for where to go if home cooling fails, and familiarity with heat illness symptoms are foundational steps that apply every summer season, not just during active warnings. If you have not already identified a cooling location, reviewed your household’s heat plan, or checked on neighbors who are elderly or without air conditioning, August 20, 2026, is the right moment to do it.

This warning remains active through August 23, 2026, at 8:00 p.m. MST. Monitor updates directly through the National Weather Service at weather.gov or through your local NWS office for any changes to the warning scope or expiration.

For the fundamentals that apply beyond this specific alert, see our Extreme Heat Preparedness guide.

Source: National Weather Service (NWS Phoenix AZ, NWS Tucson AZ, NWS Las Vegas NV, NWS Flagstaff AZ). Active alert data retrieved 2026-08-20 22:00 UTC via api.weather.gov.