Map shows which states are facing dangerous heat
The NWS said the remainder of the week features a "strengthening heat dome over the Mississippi Valley today that gradually builds east towards the East Coast by week's end." The weather service said a combination of mid-upper 90s temperatures and humid conditions are a recipe for "oppressive heat indices that range between 110-115 degrees for many areas along and east of the Mississippi River" on Wednesday.
By Thursday, July 24, the NWS says the footprint of heat is expected to move east into the Great Lakes and Northeast regions.
"While this is not really a record-breaking air mass in terms of high temperatures, some towns and cities will struggle to drop below 80 degrees at night due to the high humidity levels and retention of heat by vast areas of concrete and pavement," AccuWeather Senior Meteorologist Brett Anderson said Wednesday. "For those that only have a fan or open window to keep cool, sleeping will be difficult for some, with a high risk of dehydration."
AccuWeather says temperatures will reach 100 degrees from Texas to western Tennessee "just about every day" for the next week or two.
See which areas are facing heat and humidity this week.
Heat wave affects nearly 100 million: Heat advisories abound as almost 100 million Americans face 'ridiculous' temps
National heat index map: See which states feel hottest
The map below identifies areas where the heat index is forecasted to reach NWS-defined levels from "Caution" (80 degrees Fahrenheit) to "Extreme Danger" (above 125 degrees).
The heat index measures how hot it actually feels when factoring for humidity. Prolonged exposure to a heat index above 80 degrees can lead to fatigue, as previously reported by USA TODAY. As it gets hotter, the risk continues to increase − potentially resulting in heat stroke or even death. Older adults, children, and outdoor workers are generally at higher risk of heat-related incidents.
What is an extreme heat advisory?
The weather service issues an Extreme Heat Warning when "extremely dangerous" heat conditions are expected or occurring. People in those areas are urged to avoid outdoor activities, especially during the heat of the day, and to check on family and neighbors.
An Extreme Heat Watch is issued when conditions are favorable for an extreme heat event but its occurrence and timing are uncertain. People are warned to suspend all major outdoor activities if a warning is issued.
What is a heat dome?
Heat dome is not actually a scientific term, according to climatecheck.com, which says the term does effectively describe the "oppressive" high-pressure atmospheric systems that cause warm air to be pushed to the Earth's surface and trapped there for long periods of time.
"The dome traps high-pressure air in one place, like the lid on a pot," the website says. "These large zones of hot air result in a combination of blistering temperatures, devastating wildfires, and drought conditions."
Gabe Hauari is a national trending news reporter at USA TODAY. You can follow him on X @GabeHauari or email him at Gdhauari@gannett.com.
This article originally appeared on USA TODAY: Heat index map: See which states will be the hottest today
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