South sweating out the 'ridiculous' heat: See who is next in triple digits
- A heat dome is descending on a swath of the nation and will slowly spread toward the East.
- Temperatures will reach 100 degrees in some areas and feel even hotter.
Almost 100 million Americans were under National Weather Service extreme heat warnings, watches or advisories July 23 as a heat dome descended on a swath of the nation and slowly spread toward the East.
The high temperature in St. Louis on July 23 was forecast at 98 degrees − and a heat index could reach a stunning 116, the weather service said. The forecast high in Little Rock for July 23-24 was 101 degrees and heat index values could near 110. The heat index measures how hot it actually feels when factoring for humidity.
It's summer and it's supposed to be hot. But temperatures will run 5-15 degrees above the historical average, AccuWeather says.
The heat dome is "not really a record-breaking air mass" that would shatter records for high temperatures, AccuWeather Senior Meteorologist Brett Anderson said. But low temperatures in many cities and towns "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," he said.
The weather service forecast for Chicago calls for a heat index of 104 on July 23 and 106 on July 24. Parts of Texas, Arkansas and Louisiana will peak at near or above 100 degrees, and much of the South, Midwest and Great Lakes will see the heat index exceed 100.
"Just absolutely ridiculous heat index values here of well over 100 degrees, and 110," Weather Channel meteorologist Jim Cantore said. "We have the combination of high temperatures, 90s in most of these cases, even 100 ... with surging moisture, deep moisture and dew points in the 80s. That's not air you can wear anymore, that is air that is going to give you a shower."
Developments:
∎ The heat dome on Wednesday covered a wide slice of the nation from Minneapolis to New Orleans and from Kansas City to Cleveland.
∎ Heavy rains and flash flooding are possible across the Missouri River Valley and Upper Midwest and Great Lakes area July 23-24, the weather service said.
∎ Tropical moisture could produce torrential downpours across portions of the Southeast. The heaviest rainfall will likely occur along the central Gulf Coast and across much of Florida through July 24.
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). Prolonged exposure to a heat index above 80 degrees can lead to fatigue. As it gets hotter, the risk continues to increase − potentially resulting in heatstroke or even death. Older adults, children, and outdoor workers are generally at higher risk of heat-related incidents.
Heat threatens power supply in China
China warned July 23 that power supply disruptions could result as people struggled to keep cool in record heat baking the nation. High temperatures have exceeded 100 degrees almost daily for the last two weeks across much of the sprawling country of 1.4 billion people, also spurring warnings to the elderly to guard against heatstroke.
Since mid-March, the number of days when temperatures reached 95 or more is the highest on record, said Jia Xiaolong, deputy director of the National Climate Center.
Don't like the heat wave? Head west
While most of the nation swelters, much of the West Coast will be unseasonably cool thanks to a "meandering" low pressure system high in the atmosphere off the California coast, the weather service says. Translation: The July 24 forecast high for Chicago is 97, for Los Angeles and Seattle it is 79.
This "upper low" in the West will also trigger showers and thunderstorms in parts of northern California − and there is potential for localized flash flooding near wildfire burn scars. Mostly dry conditions are forecast for the Desert Southwest, and don't worry about being unseasonably cool in Phoenix. The high July 24 is forecast at 104.
Heat dome could linger for two weeks
The heat dome won't dissipate soon. Dangerous heat is expected across parts of the Central and Southeast. through July, the weather service says. High temperatures will reach 100 degrees from Texas to western Tennessee almost every day for a week or two, AccuWeather said.
The Northeast was given a couple days reprieve: highs in the 80s and relatively low humidity. But the dome will spread across the region July 25, driving high temperatures deep into the 90s that will feel like more than 100 degrees as the humidity builds there.
Heavy rain but probably not a hurricane
The 2025 hurricane season may be kicking into more active gear in the days ahead, and a disturbance near U.S. shores has drawn the attention of the National Hurricane Center. In a July 22 update, the hurricane center flagged a low pressure area off Northeast Florida that showed some chance of developing after it crosses over Florida into the Gulf of America, renamed from the Gulf of Mexico, later in the week.
No matter how organized the system becomes, the northern Gulf Coast faces a few more days of heavy rain, forecasters say.
"Expect rain and storm chances to increase toward the end of the week as this disturbance moves in, though it's too early to say much with certainty beyond that," the National Weather Service office in Houston posted on its social media.
− Dinah Voyles Pulver
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.
A heat advisory is issued for dangerous heat conditions that are not expected to reach warning criteria.
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."
Contributing: Gabe Hauari