A dangerous stretch of extreme heat is spreading across parts of the Southwest, with National Weather Service warnings covering communities in Arizona, California, and Nevada as temperatures climb well into the triple digits.
In some of the hottest areas, afternoon temperatures could reach 118°F. The National Weather Service office in Phoenix says portions of southwest Arizona and southeast California are under an Extreme Heat Warning through Saturday evening, with highs expected to range from 107°F to 118°F. Another warning covering parts of northwest Arizona, southeast California, and southern Nevada calls for temperatures of 115°F to 118°F around Death Valley and the Colorado River Valley through Friday.
The 118°F figure does not mean every city under a warning will get that hot. Phoenix, for example, is expected to see afternoon temperatures in the 108°F to 116°F range, while the current forecast for Yuma peaks closer to the mid-110s. The most extreme readings are expected in the hottest desert locations.
Extreme Heat Could Last Through the Week
This is not a warning for a single hot afternoon. Much of the affected region is facing several consecutive days of dangerous temperatures, with overnight lows remaining unusually warm in some desert communities.
The National Weather Service says the Phoenix metropolitan area is under an Extreme Heat Warning through 8 p.m. Saturday, August 29. Phoenix, Mesa, Tempe, Scottsdale, Chandler, Gilbert, Glendale, Peoria, Goodyear, and surrounding communities are among the areas included, with afternoon highs of 108°F to 116°F possible. Farther west, the warning includes Yuma, El Centro, Brawley, Calexico, Blythe, Parker, Quartzsite, and other communities where the upper end of the forecast reaches 118°F.
Warm nights add to the problem because the body and buildings have less time to recover before temperatures rise again. In some desert valleys covered by the warnings, overnight lows are expected to remain in the upper 80s or even lower 90s, making reliable air conditioning especially important.
Heat Exhaustion Can Turn Serious Quickly
Extreme heat can affect people who are otherwise healthy, particularly during prolonged outdoor activity. The risk is higher for older adults, young children, outdoor workers, people without dependable air conditioning, and those with certain medical conditions.
Heat exhaustion can cause heavy sweating, weakness, dizziness, headache, nausea, muscle cramps, and fainting. The CDC recommends moving to a cooler place, loosening clothing, using cool wet cloths or a cool bath, and sipping water. Medical attention is recommended when symptoms worsen, vomiting occurs, or symptoms continue for more than an hour.
Heat stroke is much more serious. Warning signs can include confusion, loss of consciousness, a very high body temperature, dizziness, nausea, and hot or red skin. The CDC says heat stroke is a medical emergency and 911 should be called immediately. Concerns about emergency room costs, medical bills, or health insurance coverage should not delay emergency medical care when heat stroke is suspected.
Outdoor Workers Face an Especially High Risk
People working construction, landscaping, delivery routes, agriculture, roofing, and other outdoor jobs can spend hours exposed to temperatures that most residents encounter only briefly.
OSHA recommends a simple combination of water, rest, and shade, but the details matter as temperatures rise. Workers should have cool drinking water available and should drink regularly rather than waiting until they feel thirsty. Longer jobs may also require electrolyte-containing drinks because sweating removes salt and other electrolytes from the body. Rest periods should become more frequent as heat stress increases, and breaks should be taken in shaded or air-conditioned areas whenever possible.
The National Weather Service is also advising people to move strenuous activity to the early morning or evening when possible. Anyone overcome by heat should be moved to a cooler location, and heat stroke requires emergency help.
Your Air Conditioner Matters More During a Multi-Day Heat Wave
A working air-conditioning system can become a safety issue when temperatures remain above 110°F for several days. Homes that normally cool down at night may remain hot around the clock, especially when overnight temperatures stay in the 80s and 90s.
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Residents who have noticed problems with their air conditioner may want to address them before the hottest part of the week rather than waiting for a complete breakdown. HVAC repair companies can become busier during major heat events, and even a short loss of cooling can be difficult for older adults or anyone who is particularly sensitive to heat.
People without working air conditioning should consider spending the hottest hours in a cooled public location rather than trying to tolerate dangerous indoor temperatures. Maricopa County’s 2026 Heat Relief Network is operating through September 30 and includes free cooled spaces and other heat-relief resources around the Phoenix area.
Higher Energy Bills Can Become Another Problem
Running air conditioning for longer periods can also push up household energy costs, particularly during a prolonged heat wave when cooling systems may operate through much of the day and night.
Arizona residents struggling with cooling bills may have financial assistance options. The state’s Low Income Home Energy Assistance Program, or LIHEAP, helps eligible low-income households with heating and cooling costs, while Arizona’s newer Power AZ program expands utility assistance to additional households. The Arizona Department of Economic Security says households approved for LIHEAP or Power AZ on or after March 23, 2026, may also qualify automatically for supplemental utility assistance payments.
That assistance can matter during a heat emergency because cutting back on air conditioning simply to lower an electric bill may not be safe when temperatures are approaching 110°F or higher. Residents facing high energy bills should check eligibility before assuming that utility assistance is unavailable.
Never Leave Children or Pets in a Parked Car
A vehicle can become dangerous much faster than many people expect during extreme heat. The National Weather Service warns that car interiors can reach lethal temperatures within minutes and says young children and pets should never be left unattended in a vehicle.
This remains true even when someone expects to be away from the vehicle only briefly. During a week when outdoor temperatures are already above 110°F, there is very little margin for error.
Checking on neighbors and relatives is also important, particularly people who live alone, do not have reliable cooling, or may have difficulty recognizing the effects of heat. The NWS is advising residents in affected areas to stay hydrated, remain in air-conditioned spaces when possible, stay out of direct sun, and monitor local warnings as conditions change.
The 118°F Forecast Is Not for Everywhere
The headline number is alarming, but location matters. The National Weather Service’s current warnings place the 118°F upper range in some of the hottest desert portions of the Southwest, not across every city under an Extreme Heat Warning.
Phoenix could still reach as high as 116°F under the current warning, while areas around the Colorado River Valley and Death Valley could approach 115°F to 118°F. Yuma is included in a warning zone where temperatures could range from 107°F to 118°F, although its city forecast currently peaks below the very top of that range.
Warnings also end at different times depending on location. Some areas remain under an Extreme Heat Warning through Friday evening, while the Phoenix, Yuma, and southeast California warning continues through 8 p.m. Saturday, August 29. Forecasts and warnings can be changed as new data comes in, so residents should continue checking the National Weather Service rather than relying on a forecast seen several days earlier.
For anyone in the affected region, the practical message is straightforward: several days of unusually dangerous heat are ahead. Staying inside during the hottest hours, keeping the home safely cooled, drinking enough water, knowing the signs of heat illness, and finding cooling or utility assistance early can make a major difference before temperatures reach their peak.
