(NEW YORK) --A dangerous heat wave is bringing prolonged extreme heat to the Midwest, the South and the East Coast this week.

The extreme heat hit the Midwest first. On Monday, the heat index -- what temperature it feels like with humidity-- soared to the triple digits in Minneapolis and Chicago.

On Tuesday, the worst of the heat will stretch from the Great Lakes to the South to the central Gulf Coast.

The heat index is forecast to hit 105 degrees in Chicago, 111 in Detroit, 110 in Louisville, Kentucky, 106 in Little Rock, Arkansas, and 105 in Houston.

Chicago has activated cooling centers throughout the city, including at community service centers, senior centers, libraries, city colleges and police districts. Chicago Public Schools said all summer programming will be inside Monday through Wednesday.

On Wednesday, the heat will continue in the Midwest and the South and also spread into the Northeast.

The heat index is forecast to reach a scorching 108 degrees in Detroit, 105 degrees in Houston, 102 in New York City, and 104 in Philadelphia and Washington, D.C.

The heat will stay in place in the Great Lakes and the South Thursday, with temperatures climbing even higher in the Northeast. The heat index could hit 107 degrees in New York City, 111 in Philadelphia and 110 in Washington, D.C.

There will be minimal relief overnight, which makes the heat even more dangerous.

The unrelenting heat continues Friday with the heat index forecast to reach 102 in Detroit, 106 in Memphis, Tennessee, 102 in Tampa, Florida, and 109 in New York, Philadelphia and Washington, D.C.

Extreme heat is considered the deadliest weather-related hazard in the U.S. At least 13,000 Americans have died from heat since 2018, according to the Centers for Disease Control and Prevention.

On the Fourth of July on Saturday, the heat index will remain dangerously high, forecast to hit 104 in New York, 109 in Washington, D.C., and 108 in Philadelphia.

Click here for tips on how to stay safe.

ABC News' Dan Peck and Michelle Simmons contributed to this report.

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