On July 28, millions of Americans remained under extreme heat warnings as a powerful heat dome continued to grip much of the central and southern United States, driving temperatures well above seasonal averages and creating dangerous conditions across dozens of states.
The National Weather Service warned that at least 40 million people were under extreme heat alerts, with heat index values exceeding 100 degrees Fahrenheit (38° C) from Minnesota south to Mississippi and stretching westward into California and Nevada. Parts of the Desert Southwest were expected to experience temperatures approaching 120° F (49° C).
Meteorologists attributed the prolonged heat to a “heat dome”—a large area of high atmospheric pressure that traps hot air near the surface, suppresses cloud formation, and allows temperatures to build over several days. The weather pattern has fueled widespread triple-digit temperatures and unusually warm overnight lows, offering little relief after sunset.
The prolonged heat has broken or threatened temperature records in several states, including parts of the Great Plains and northern Rockies. In Rapid City, South Dakota, temperatures climbed to 112° F (44° C), setting a new daily record. Forecasters warned that additional records could be challenged as the heat spreads eastward during the week.
Americans urged to limit outdoor activity
Health officials urged residents to limit outdoor activity during the hottest parts of the day, remain hydrated, and seek air-conditioned spaces whenever possible. The National Weather Service said the greatest risk is for older adults, young children, outdoor workers, and people with chronic medical conditions, particularly as high overnight temperatures reduce the body’s ability to recover from daytime heat.
Success
You are now signed up for our newsletter
Success
Check your email to complete sign up
Several communities opened cooling centers as emergency officials responded to the prolonged heat. The oppressive conditions also forced the cancellation or postponement of some outdoor events, including horse racing in Minnesota, while utilities monitored electricity demand as air-conditioning use surged.
Forecasters said parts of the Midwest may see some relief later this week as a cold front pushes through, but much of the southern United States is expected to remain under dangerous heat into the weekend.
Climate scientists noted that while heat domes are a naturally occurring weather phenomenon, rising global temperatures have increased the likelihood and intensity of extreme heat events. The first half of 2026 ranked as the second hottest on record for the contiguous United States, continuing a broader trend toward more frequent and prolonged heat waves.
Health impacts
Although hurricanes, tornadoes, and floods often receive greater public attention, extreme heat consistently causes more weather-related deaths in the United States than any other natural hazard.
According to the U.S. National Weather Service and the Centers for Disease Control and Prevention (CDC), hundreds of people die each year from heat-related illnesses, while many more require emergency medical treatment during prolonged periods of extreme heat.
Health officials warn that the danger extends well beyond daytime temperatures. During major heat waves, nighttime temperatures often remain unusually high, preventing the human body from cooling and recovering after prolonged exposure to the heat. Several consecutive nights of warm temperatures can significantly increase the risk of heat-related illness, particularly for people without access to air conditioning.
The greatest risk is faced by older adults, infants and young children, people with chronic heart or lung disease, outdoor workers, athletes, and those taking medications that affect the body’s ability to regulate temperature. Urban residents are also especially vulnerable because concrete, asphalt, and buildings absorb heat during the day and release it slowly overnight, creating what is known as the “urban heat island” effect.
Medical experts advise anyone experiencing heavy sweating, dizziness, weakness, nausea, muscle cramps, or fainting to seek a cool environment immediately, as these can be early signs of heat exhaustion. If left untreated, heat exhaustion can rapidly progress to heat stroke—a life-threatening medical emergency marked by a body temperature above 104° F (40° C), confusion, loss of consciousness, or seizures. Heat stroke requires immediate emergency medical attention and can cause permanent organ damage or death if not treated promptly.
