Dangerous heat to head to Northeast after slamming Midwest, South

Extreme heat is gripping the Midwest and the South on Tuesday before moving into the Northeast on Wednesday.

Record-high temperatures were shattered across the Midwest on Monday, including in Waterloo, Iowa, which reached a scorching 98 degrees.

On Tuesday, 14 states from Iowa to New York are on alert for dangerous heat.

In Detroit, public school students are being released three hours early on Tuesday due to the heat.

The heat index -- what temperature it feels like with humidity -- is forecast to soar Tuesday to 110 degrees in Chicago; 101 degrees in Indianapolis and Nashville, Tennessee; 100 in Louisville, Kentucky; and 98 in Pittsburgh.

On Wednesday, the heat will spread into the Northeast.

Washington, D.C., could reach a record high of 99 degrees with a heat index of 104 degrees. The heat index could reach 105 degrees in Philadelphia and 99 in New York City.

On Thursday, the record heat will end for the Midwest and the Northeast, but will continue for the South.

Actual temperatures of 101 degrees and 97 degrees are forecast for Nashville and Atlanta, respectively.

There are hundreds of deaths each year in the U.S. due to excessive heat, according to CDC WONDER, an online database, and scientists caution that the actual number of heat-related deaths is likely higher.

Last year marked the most heat-related deaths in the U.S. on record, according to JAMA, a peer-reviewed medical journal published by the American Medical Association.

Click here for tips on how to stay safe in the heat.