Heat Dome Sends 'Feels Like' Temperatures Soaring Across 19 States
A sprawling heat dome has settled over the central United States, driving actual temperatures well above 100°F and pushing the heat index — the "feels like" temperature — to life-threatening levels. As of July 30, 2026, the National Weather Service has issued extreme heat warnings for parts of 19 states, from California and Arizona to Minnesota and Tennessee, affecting roughly 70 million people.
In Morton, Minnesota, the heat index reached a staggering 123°F on Sunday, July 26, while Sanborn recorded 122°F and New Ulm hit 120°F, according to local reports. Farther south, Dallas-Fort Worth saw a heat index of 112°F on Tuesday, July 21, with triple-digit actual temperatures. The oppressive conditions are not letting up overnight: lows are expected to remain in the 80s and even low 90s in some areas, preventing the body from recovering and increasing cumulative heat stress.
The heat dome — a strong, stationary area of high pressure that traps hot air near the ground — is forecast to linger through at least the first week of August. The National Weather Service has warned that the combination of high temperatures and humidity creates a high risk of heat-related illnesses, especially for vulnerable populations such as the elderly, children, and outdoor workers.
What Exactly Is the Heat Index?
The heat index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. It is sometimes called the "apparent temperature" or "feels-like" temperature. The human body cools itself by sweating, which evaporates from the skin. However, when humidity is high, sweat evaporates more slowly — or not at all — making it harder for the body to regulate its internal temperature. This can lead to heat exhaustion, heat stroke, and even death.
The National Weather Service calculates the heat index using a complex formula that accounts for temperature and relative humidity. For example, when the actual temperature is 95°F and the relative humidity is 55%, the heat index is 108°F. At a heat index of 105°F or higher, the NWS warns that heat stroke is possible with prolonged exposure.
During the current heat dome, actual high temperatures across the affected region range from around 97°F in St. Cloud, Minnesota, to 108°F to 116°F in Arizona and southern Nevada. But with humidity in the mix, heat index values are often 10 to 20 degrees higher than the actual temperature. In parts of Tennessee, Arkansas, Mississippi, Missouri, Illinois, Iowa, Kansas, Nebraska, and Oklahoma, the heat index has reached between 110°F and 117°F.
Why This Heat Dome Is Particularly Dangerous
Meteorologists classify the current event as a particularly dangerous heat dome because of its size, duration, and intensity. The high-pressure system is acting like a lid on a pot, compressing and warming the air as it descends, suppressing rain clouds, and allowing temperatures to build day after day.
In Texas, cities like San Antonio are bracing for what forecasters call "the hottest week of the year so far." The heat dome is expected to bring triple-digit temperatures across much of the state, with heat index values reaching 100°F to 105°F. The National Weather Service has raised the Heat Risk level for parts of South Texas to Level 3 and Level 4 out of 4 by Friday, indicating extreme risk of heat illness.
In Minnesota, where the heat index hit 123°F in some locations, even northern states that are unaccustomed to such extreme heat are feeling the effects. St. Cloud recorded its warmest day of the year on July 26, with an actual temperature of 97°F, marking the 10th day of 90-degree weather this summer.
Overnight lows in many areas are not expected to drop below the 80s, and in some cases the low 90s, providing little relief and allowing heat stress to accumulate. People living in mobile homes, older homes without air conditioning, or in urban heat islands are especially at risk. Extreme heat warnings remain in effect across the Southwest, where Phoenix recently broke a record at 117°F.
What Is a Heat Dome and How Does It Form?
A heat dome develops when a large, strong area of high pressure parks over a region for an extended period. According to NOAA, the high-pressure system acts like a lid on a pot, trapping hot air near the surface and preventing it from rising and cooling. The sinking air compresses and warms further, creating a feedback loop that intensifies the heat.
In San Antonio, meteorologists describe the subtropical high as a "lid" that suppresses cloud formation and allows the sun to heat the ground day after day. This pattern is common in summer across the southern United States, but this year's heat dome is unusually persistent and broad.
The heat dome has been linked to climate change, as warmer global temperatures make such events more intense and longer-lasting. While heat waves have always occurred, the frequency of extreme heat events has increased in recent decades, and the 2026 event fits that trend.
Health Risks and Safety Tips
Extreme heat is the deadliest weather-related hazard in the United States, killing more people annually than hurricanes, floods, or tornadoes. The current heat dome poses a serious threat to public health, with heat-related illnesses such as heat exhaustion and heat stroke becoming more likely as the heat index climbs above 100°F.
Symptoms of heat exhaustion include heavy sweating, weakness, dizziness, nausea, and headache. If untreated, it can progress to heat stroke, which is a medical emergency characterized by a body temperature above 103°F, hot red skin, rapid pulse, and altered consciousness. Heat stroke can cause permanent damage or death if not treated promptly.
The National Weather Service advises people to stay out of the sun during the hottest part of the day (usually 10 a.m. to 4 p.m.), drink plenty of water, wear lightweight and light-colored clothing, and take frequent breaks in air conditioning. Check on elderly neighbors and relatives, and never leave children or pets in parked cars, even for a few minutes. Flash flood warnings have also been issued in some areas, adding to the danger.
Broader Implications and Trends
The 2026 heat dome is a stark reminder that extreme heat events are becoming more common and more severe. Climate models have long predicted that heat waves will intensify as global temperatures rise, and this year's event appears to fit that pattern. Record-breaking temperatures in 2023 and 2024, followed by another major heat dome in 2026, suggest that the United States is entering a new era of dangerous summer heat.
Economically, the heat dome is disrupting daily life, reducing productivity in outdoor industries such as agriculture and construction, and straining power grids as demand for air conditioning surges. States like Texas and California have already called for voluntary conservation measures to avoid blackouts.
The human cost is also rising. The elderly, children, and low-income communities that lack access to air conditioning are the most vulnerable. As heat waves become more frequent, cities are investing in cooling centers, tree canopy programs, and emergency response systems to protect residents.
While the heat dome is expected to weaken by the weekend of August 8, forecasters warn that high temperatures may return quickly. For now, the message from meteorologists is clear: stay cool, stay hydrated, and stay safe.
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