More than 150 million Americans are under the highest-level extreme heat alerts during a wave of above-average temperatures.

After topping 90 degrees June 21 for the first time this year, temperatures in Indianapolis will continue to climb for the next two days.

"A dangerous, widespread heat wave will bake the central and eastern U.S., bringing the hottest temperatures of the year and uncomfortably muggy air to the Midwest and Northeast that in some areas could last into much of next week,