August 25, 2026 — A powerful and unusually persistent heat dome is expanding westward across the United States, pushing temperatures to dangerous levels from Texas and Oklahoma toward New Mexico, Arizona and California.
Meteorologists say the heat is expected to remain intense through the end of August and could continue into early September, creating a prolonged threat to public health, electricity systems, outdoor workers and wildfire conditions.
The extreme weather is already challenging long-standing temperature records. Dallas tied its hottest day on record Monday, while Oklahoma City reached 108 degrees Fahrenheit, tying its daily record. Near Chickasha, Oklahoma, temperatures climbed as high as 115 degrees.
The heat is now shifting westward, with some of the most dangerous conditions expected across the Desert Southwest and Southern California.
Heat Dome Moves From Texas Toward California
A heat dome occurs when a strong area of high pressure settles over a region and effectively traps hot air beneath it. Instead of allowing cooler air to replace the heat, the atmospheric pattern can persist for days or even weeks.
That is what is happening across much of the southern United States.
The center of the current heat is expected to gradually move toward New Mexico, Arizona and Southern California. Forecasters expect numerous locations to approach or exceed daily temperature records as the heat intensifies.
The forecast is particularly concerning because the event is not simply producing one or two exceptionally hot afternoons. The duration of the heat is becoming one of its defining characteristics.
Dallas Nears a Historic August
Dallas is already experiencing an extraordinary month.
On Monday, the city recorded an average temperature of 97.5 degrees Fahrenheit, tying its hottest overall day on record. The daytime temperature reached 109 degrees after an overnight low of 86 degrees.
By the end of August, Dallas could record temperatures of at least 100 degrees on 27 of the month's 31 days. That would come within one day of the city's August record of 28 such days, established in 2011.
The persistence of the heat is particularly significant because nighttime temperatures are also remaining unusually high.
When temperatures fail to fall substantially after sunset, the human body has less opportunity to recover from daytime heat exposure. Homes and buildings can also retain heat, making it harder for people without reliable air conditioning to cool down.
Oklahoma Is Also Breaking Heat Records
Oklahoma has experienced similarly extreme conditions.
Oklahoma City reached 108 degrees Monday, tying its daily record. The city has now reached at least 100 degrees on 18 days this month.
The August record is 20 days, set in 2011, meaning only a few additional triple-digit days could establish a new benchmark.
The most extreme temperature Monday occurred near Chickasha, southwest of Oklahoma City, where temperatures reached 115 degrees.
These temperatures are dangerous even for communities accustomed to hot summers because prolonged exposure increases the cumulative stress on people, infrastructure and ecosystems.
California and Arizona Face the Next Surge
As the heat dome moves west, the focus is shifting toward the Southwest.
Forecasters expect some exceptionally high temperatures Wednesday and Thursday, including:
122°F in the hottest parts of Death Valley, California
116°F in Yuma, Arizona
115°F in El Centro, California
114°F in Phoenix
109°F in Las Vegas and Tucson
107°F in Palmdale, California
101°F in downtown Los Angeles
Several of these temperatures could challenge or break existing records for this time of year.
Death Valley is particularly vulnerable because of its already extreme desert climate. A forecast temperature around 122 degrees would place conditions among the most dangerous levels experienced anywhere in the country.
Southern California Faces Unusual Humidity
The heat is not the only concern for California.
Southern California has also been experiencing unusually high humidity, making the current event different from the dry heat many residents typically associate with the region.
Meteorologists say an exceptionally warm marine environment in the Pacific Ocean has contributed additional moisture to the atmosphere. Dew points around Southern California have been approaching 70 degrees, an unusually high level for the region.
That moisture can make extreme heat more dangerous because high humidity reduces the body's ability to cool itself through evaporation of sweat.
The result can be oppressive conditions even after the sun goes down.
Nights May Be Almost as Dangerous as Days
One of the most concerning characteristics of this heat wave is the lack of nighttime relief.
Meteorologists expect overnight temperatures to remain unusually high across large parts of the Southwest.
In Southern California, temperatures may remain above 70 degrees overnight for several consecutive days in many areas. Lake Havasu City, Arizona, could see a low around 93 degrees Thursday, while Palm Springs, California, could remain near 89 degrees.
Such conditions can make it difficult for people to recover from daytime heat.
For vulnerable residents—including older adults, young children, people working outdoors and those without effective cooling—the combination of high daytime temperatures and warm nights can significantly increase health risks.
Nearly 100 Million Americans Face Major Heat Risks
The scale of the event is enormous.
NOAA's HeatRisk system indicates that roughly 98 million Americans could experience major or extreme heat-related risks through the end of August, with the greatest concentrations extending from the Southwest and southern Plains into Texas.
Extreme heat can increase the likelihood of dehydration, heat exhaustion and potentially fatal heatstroke.
People who work outside face particular risks because they may spend many hours exposed to temperatures that would be dangerous even during shorter periods.
Health officials generally emphasize hydration, access to air conditioning or other cooling environments, limiting strenuous outdoor activity during the hottest part of the day and checking on vulnerable family members and neighbors.
Wildfire Threat Could Also Increase
The heat dome is creating concerns beyond human health.
Extended extreme heat can dry vegetation and soils, increasing wildfire risks in areas where fuels are already dry.
Climate scientist Daniel Swain warned that the event could produce significant impacts both from a human-health perspective and potentially from wildfire.
The combination of high temperatures, dry vegetation and difficult nighttime recovery can create particularly challenging conditions for firefighters.
In some areas, heat can also worsen drought conditions by increasing evaporation and placing additional stress on water resources.
Climate Change Adds Another Layer
The current heat dome is a specific weather event, but scientists say the broader warming climate is important when considering why extreme heat events are becoming more consequential.
According to NOAA data cited by The Washington Post, the United States has experienced roughly 21 high-temperature records for every monthly low-temperature record this year.
That imbalance reflects a long-term warming trend.
Scientists have also found that heat waves in the Southwest are becoming more frequent, more intense and longer-lasting. NASA researchers have previously linked the increasing severity of prolonged Southwest heat to human-caused climate change, while emphasizing that individual weather events are produced by multiple interacting factors.
In other words, climate change does not create every heat dome, but a warmer baseline can make extreme heat events hotter and increase the likelihood of records being broken.
When Will the Heat Finally Break?
There is little immediate relief in sight.
Forecast guidance indicates that the heat dome could remain influential through the end of August, with some impacts continuing into early September. The center of the extreme heat is expected to shift westward rather than simply disappear.
That means different regions may experience the worst conditions at different times.
Texas and Oklahoma are dealing with the current peak, while Arizona, New Mexico and California are preparing for another surge.
The prolonged nature of the event is ultimately what makes it so concerning. Individual days above 100 degrees are not unusual across the Southwest, but repeated extreme temperatures combined with unusually warm nights can place sustained pressure on people and infrastructure.
A Dangerous End to August
The expanding heat dome is turning the final days of August into a potentially historic period of extreme weather across the southern and western United States.
From Dallas and Oklahoma City to Phoenix, Las Vegas, Los Angeles and Death Valley, communities are facing temperatures capable of challenging records.
And because the heat is expected to persist, the danger cannot be measured simply by the highest temperature reached on a single afternoon.
The combination of extreme daytime heat, unusually warm nights, humidity, wildfire concerns and prolonged exposure is what makes this event particularly dangerous.
For millions of Americans, the message from forecasters is clear: this is not simply another hot spell. It is a long-lasting heat event whose most intense phase is now spreading west—and the records may continue to fall before the heat finally breaks.
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