The National Weather Service has issued extreme heat warnings across 12 states as a massive week-long heat dome pushes heat index values to 115 degrees Fahrenheit.
Forecasters warned that conditions across the region are roughly 20 degrees hotter than the Sahara Desert, creating dangerous conditions expected to last through Monday night.
The extreme heat warnings cover Arkansas, Louisiana, Mississippi, Alabama, Tennessee, Florida, Georgia, and the Carolinas. A massive high-pressure system positioned over the Gulf Coast has locked in extreme heat and humidity since last week, driving up real-feel temperatures throughout the Southeast and Gulf states.
Forecasters with AccuWeather predicted actual high temperatures in several major cities, including Little Rock in Arkansas, Charleston in South Carolina, and Jacksonville in Florida, will approach 100 degrees Fahrenheit. The oppressive combination of heat and humidity threatens to push the local heat index into a lethal zone for residents.
Weather officials urged people living under the heat dome to stay indoors in air-conditioned spaces whenever possible, particularly during the afternoon and evening hours on Monday. Prolonged outdoor exposure in such high temperatures can quickly trigger dehydration and severe illness.
High pressure and extreme heat indices
Meteorologists describe a heat dome as a persistent high-pressure weather system that traps high temperatures and humidity over a large geographical region, functioning much like a steam cooker. The heat index represents the feel-like temperature experienced by the human body when air temperature combines with relative humidity.
On a 90-degree day, high atmospheric humidity can elevate the feels-like temperature to 105 degrees Fahrenheit. Under the current weather pattern, the entire region is roughly 20 degrees warmer than conditions in the Sahara Desert, which is forecasted to reach only the 80s and 90s on Monday. Authorities have issued extreme heat warnings across the Southeast, urging 100 million people to avoid outdoor activity on August 17.
National Weather Service officials warned that the trapped heat and humidity make sitting inside a locked vehicle fatal within a matter of minutes, creating an acute risk for young children and pets left unattended.
AccuWeather Senior Meteorologist Brett Anderson highlighted the speed at which extreme heat poses a danger to human health. "This is the type of heat that can quickly lead to heat exhaustion or worse if proper precautions are not taken," Anderson said in a statement.
Alongside extreme heat warnings, the National Weather Service issued heat advisories across Texas, Oklahoma, and Missouri, where heat index values are also expected to reach triple digits. In total, 12 states are expected to see the heat index approach 115 degrees Fahrenheit on August 17.
Deadly health risks in Mississippi
The nearly three million people living in Mississippi sit in the direct center of the heat dome. Almost the entire state is under an extreme heat warning that will remain in effect until Tuesday or Wednesday.
The National Weather Service issued an urgent statement detailing the hazard for Mississippi residents. "There is an elevated to significant threat for dangerous heat to continue today as heat index values approach 115 and actual air temperatures reach the 100 to 104 degree range," NWS officials wrote, warning that "heat stroke [is] increasingly likely with prolonged outdoor activity."
Medical experts note that heat stroke is a far more deadly medical emergency than heat exhaustion and can develop within 15 minutes of extreme outdoor exposure. Early symptoms include a throbbing headache, confusion, slurred speech, nausea, dizziness, and a fever exceeding 103 degrees Fahrenheit. Sufferers may present with red, dry, or damp skin, a rapid pulse, and loss of consciousness before the condition turns fatal as body organs fail.
Dr Omer Awan of the University of Maryland School of Medicine previously told the Daily Mail that humidity, defined as the measure of water vapor present in the air, represents the most hazardous element of heat waves in the American South. "The more humid it is, the less likely we are to sweat, and then that can make us more prone to heat-related illnesses as well," Dr Awan explained, adding that "all these things can happen not in hours, but in minutes if you're exposed to extreme heat outside."
Nighttime heat and summer trends
AccuWeather warned that affected communities will find little relief after dark. Nighttime temperatures are forecasted to remain around 85 degrees Fahrenheit, especially in heavily developed urban areas where asphalt and concrete store heat.
Officials from the National Weather Service in Mississippi urged residents to take immediate preventive steps. "Take extra precautions when outside. Wear lightweight and loose-fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke," NWS officials recommended.
The current heat dome represents at least the third major heat event to strike the United States this year. Cities across the American Southwest and along the East Coast have repeatedly broken daily high-temperature records throughout the summer season.
