Forecast Heat and Humidity to Reach 100s in Eastern U.S. This Week

A long and dangerous heat wave is forecast to affect a large swath of the United States this week, the National Weather Service said. Temperatures are rising ahead of the July Fourth holiday, with high humidity arriving alongside the heat. A heat dome is expected to build over the eastern two-thirds of the country, CBS News meteorologist Nikki Nolan said.

Are among cities expected to see record highs into the 100s. More than 100 record highs and about 250 record-warm overnight lows are expected through Saturday night. Extreme heat warnings are in effect for Nashville, St.

Louis, Cincinnati, Kansas City, Des Moines, Chicago and Detroit. Extreme heat watches cover much of the Northeast, where temperatures over 100 degrees are expected through Saturday. Dallas, Little Rock and Memphis will also see dangerously high temperatures.

The heat index is forecast to reach 100 to 110 degrees Fahrenheit and as high as 115 F in parts of the central and eastern U.S. High heat is forecast to last into next weekend across the Great Plains, the Southeast and the Mid-Atlantic. Almost the entire country will experience above-normal temperatures over the next week to 10 days.

Nightly lows in the 70s F will offer limited relief. In the West, the Four Corners area of Utah, Colorado, New Mexico and Arizona remains under dangerous fire weather conditions. Three firefighters died Saturday and two sustained burn injuries near the Colorado-Utah border when they were overcome by flames from fast-moving wildfires.

Severe thunderstorms remain a threat across parts of the northern Plains, Upper Midwest and New England, with flooding possible. Parts of Phoenix, Las Vegas, central Texas and much of the Southwest were already experiencing temperatures around 100 degrees. The heat comes after Europe has been facing a long stretch of unusually high temperatures.