Hundreds of people die each year in the United States due to extreme heat.
Thirteen eastern states from Massachusetts to Kentucky are on alert for more extreme heat before dangerous temperatures move to the South and West.
Record temperatures were broken across New England on Thursday, including 99 degrees in Manchester, New Hampshire, 98 degrees in Hartford, Connecticut and 97 degrees in Augusta, Maine.
On Friday, temperatures are expected to reach a sweltering 98 degrees in Louisville, Kentucky; 84 degrees in Indianapolis; 96 degrees in Pittsburgh and Washington, DC; 95 degrees in Philadelphia; and 92 degrees in New York City.
In Philadelphia, this could be the longest stretch of temperatures above 32 degrees at the start of this season in 30 years.
This weekend the heat will spread to the south.
Temperatures in Washington, DC, could reach over 100 degrees Fahrenheit this weekend, marking the first time in 12 years that the city has reached triple-digit temperatures in June.
In Little Rock, Arkansas, record highs are possible through Monday.
The dangerous heat is also returning to the West this weekend: heat warnings are in effect in California, Arizona and Utah.
Temperatures could rise to 43 degrees Celsius in Palm Springs, California, 46 degrees Celsius in Phoenix and 42 degrees Celsius in Las Vegas.
Hundreds of people die each year in the United States due to extreme heat, according to CDC WONDER, an online database, and scientists warn that the actual number of heat-related deaths is likely higher.
Click here for tips on protecting yourself from the heat.
