Next week’s heat wave mapped: See your state's forecast highs

An early-season heat wave is expected to build across much of the eastern United States next week, pushing temperatures into the 80s and 90s for millions of people.

The National Weather Service Weather Prediction Center says a larger weather pattern setting up over the eastern U.S. will allow heat to build and stick around for several days. That means warm air will spread from the Midwest into the East Coast and linger through midweek before a cold front moves in and brings relief late in the week.

"In the temperature department, heat will be making headlines for much of the Eastern U.S. for the first half of the week, with the hottest conditions across interior portions of the Mid-Atlantic into the Carolinas where highs are likely to reach the lower to middle 90s," the Weather Prediction Center wrote. "This will likely be warm enough to establish some daily record highs before a cold front brings relief from the Ohio Valley to the Mid-Atlantic/Northeast by Thursday."

The hot weather is being caused by a large area of high pressure sitting over the eastern U.S. This kind of setup acts like a lid in the atmosphere — it helps warm air build up near the ground and keeps clouds and storms from developing as easily.

With fewer clouds and less rain, temperatures can climb higher each day, paired with high humidity that may bring feels-like temperatures into triple digits.

Maps show how hot temperatures will get

Heat builds across the Northeast early next week, peaking Tuesday into Wednesday before a cold front brings relief by Thursday. Maps show forecast temperatures near you.

National heat index map: How hot does your city feel?

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.

Search the heat index forecast in your area

Is your city getting hotter? It's possible! You can check the heat index forecast here to find out!

What is an extreme heat warning?

The National Weather Service issues different alerts depending on how severe and certain the heat threat is, and the thresholds vary by region.

• Extreme Heat Warning — Take Action!Issued when extremely dangerous heat conditions are expected or happening. Avoid outdoor activities during the hottest part of the day, stay in air-conditioning as much as possible — even overnight — and check on family, friends, and neighbors.
• Extreme Heat Watch — Be Prepared!Issued when forecasters see the potential for extreme heat but details on timing and severity remain uncertain. Plan ahead for the possibility of suspending outdoor activities and make arrangements for a cool place to stay if you don’t have air conditioning.
• Heat Advisory — Take Action!Issued when dangerous heat is expected but conditions don’t meet warning criteria. Limit time outside, stay hydrated, and take frequent breaks in the shade or in cool spaces.

What’s the difference between temperature and heat index?

The temperature is the actual air reading — what a thermometer records in the shade. The heat index, on the other hand, represents what it feels like to the human body when both temperature and humidity are factored in, according to the National Weather Service.

When humidity is high, sweat doesn’t evaporate as easily, making it harder for your body to cool down. That’s why the heat index is often higher than the air temperature, and why it’s used to gauge the risk of heat-related illness.

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Brandi D. Addison covers weather across the United States as the Weather Connect Reporter for the USA TODAY Network. She can be reached at [email protected]. Find her on Facebook here.