Nearly 100 million under life-threatening heat dome alerts from Chicago to New Orleans

More than 97 million people are under life-threatening heat alerts from the South to the East Coast as a large ridge of high pressure builds over the central U.S. this week, commonly referred to as a heat dome.

The FOX Forecast Center said nearly 200 million people will be feeling the heat by the end of the week as the system acts like a lid on the atmosphere, trapping heat and leading to prolonged periods of hot, dry weather.

While this particular event may not break temperature records, it will still drive widespread highs into the upper 90s across a significant portion of the country. 

Adding to the discomfort will be the humidity. With elevated dew points, the heat index or “feels-like” temperature is expected to exceed 100 degrees in major cities such as St. Louis, Kansas City and Oklahoma City.

Some spots could feel closer to 110 to 115 degrees.

High humidity hinders the body’s ability to cool through sweating, making it feel significantly hotter than the actual air temperature. Beneath the heat dome, conditions will remain mostly dry. 

Texas, for instance, will continue drying out after recent flooding in places like Kerrville.

By Thursday, parts of the Great Lakes region will experience heat index values climbing into the mid- to upper 90s as dew points rise into the 70s.

The most intense heat is expected to shift toward the I-95 corridor on Friday. 

Cities from Washington to New York City and Boston will see highs well into the 90s, and when combined with a tropical air mass, it will feel like 100 degrees or more. A few daily record highs may be challenged.

Newark, New Jersey, for example, could approach the upper 90s.

Heat advisories are now in place for portions of Connecticut, Rhode Island and Massachusetts, including Boston, on Thursday through Friday.

Looking ahead to the weekend, slightly cooler temperatures are forecast for cities like New York and Boston, where highs will dip back into the 80s. 

However, the mid-Atlantic will remain under the grip of extreme heat, with heat indices staying in the lower 100s from D.C. to Richmond, Virginia.

The combination of heat and humidity could also spark a few afternoon thunderstorms.

So far this summer, more than two dozen U.S. cities are experiencing one of their top five warmest summers on record, with temperatures averaging 1 to 3 degrees above normal, the FOX Forecast Center notes.

Long-range outlooks suggest the East and Northeast will likely remain warmer than average through the remainder of the season.