Life-threatening heat dome broils millions across eastern US as records tumble

St. Louis scorching under extreme heat warnings during life-threatening heat dome

St. Louis is one of many cities feeling the heat this week. An Extreme Heat Warning is in effect until at least Wednesday. Meanwhile, people near Busch Stadium are trying to stay cool. FOX Weather Storm Specialist Mike Seidel is there with the latest temperatures. 

NEW YORK – Tuesday has been one of the worst days of a dangerous heat wave that is producing life-threatening conditions for those without access to cooling and hydration.

Nearly 160 million people across more than 25 states are under either an Extreme Heat Warning or Heat Advisory, from Florida to New England, and west through the Midwest and Mississippi Valley, even stretching to parts of northeastern Texas. 

KNOW YOUR HEAT TERMINOLOGY: EXTREME HEAT WARNING, EXTREME HEAT WATCH AND HEAT ADVISORY

New York City subway loses power amid life-threatening heat dome broiling millions across eastern US

Two New York City subway lines were shut down due to a power outage near the peak of the Tuesday morning rush as thousands of commuters dealt with near-triple-digit heat indices – the impact of a massive heat dome affecting millions of people across the eastern half of the U.S. FOX Weather Meteorologist has the latest from lower Manhattan.

In the Northeast, two New York City subway lines were shut down due to a power outage near the peak of the Tuesday morning rush as thousands of commuters dealt with near-triple-digit heat indices – the impact of a massive heat dome affecting millions of people across the eastern half of the U.S.

The extreme temperatures were being investigated as a potential cause of the New York City subway power outage. 

The president of MTA New York City Transit, Demetrius Crichlow, said these kinds of temperatures do pose a challenge for operations.

The B and C lines of the New York City Subway were suspended Tuesday morning during what is expected to be the City's hottest day of the year thus far. The outage caused a cascade of delays. 

(Stephen McCloud/FOX Weather / FOX Weather)

"The extreme temperatures can put a stress on the system," he said.

The power outage at the West 4th Street station caused a cascade of delays. The subway serves roughly 3.4 million people every day, according to the MTA. 

By Tuesday afternoon, all trains were back in service and running on delays. 

HOW TO WATCH FOX WEATHER

Dangerous heat dome continues scorching Philadelphia

Extreme heat has been baking the Eastern US, but relief isn't expected until the end of the week. FOX Weather Correspondent Katie Byrne is in Philadelphia at a splash pad where not many people were leaving the comfort of their AC to beat the heat. 

Tuesday was expected to be the hottest day of the year so far for major Northeast metropolitan areas, including Philadelphia, New York City and Boston.

Boston reached 99 degrees. An Extreme Heat Warning is in effect through Tuesday for Newark, New Jersey, just across from New York.

In fact, Tuesday set the record for third-most 100+ degree days with weeks of summer left to go. It's the most 100-degree days on record before Aug. 1. 

These dangerous conditions will persist across many of these areas before beginning to relent Wednesday, across the northern tier of the U.S.

Extreme Heat Warnings remain in effect for portions of the Southeast coast Tuesday, including parts of the Carolinas, Georgia and northern Florida. Places along the Mississippi River, including St. Louis; Memphis, Tennessee; and Jackson, Mississippi, are also under Extreme Heat Warnings.

This graphic shows heat alerts through Wednesday, July 30, 2025.

(FOX Weather)

Raleigh and Charlotte, North Carolina, as well as Atlanta, are expected to face an extreme heat risk for multiple days.

Record-high temperatures were set across several locations in Florida on Monday.

On Sunday, Tampa, Florida, soared to 100 degrees by 3:30 p.m., breaking the city’s all-time record-high temperature since recordkeeping began in 1890.

HOW TO WATCH FOX WEATHER

Florida swelters with dangerous humidity, heat across the state

FOX Weather Correspondent Brandy Campbell reports from West Palm Beach, Florida, among the cities facing a brutal combination of humidity and heat. Campbell spoke to residents who were out before the Sun to avoid the heat. Extreme Heat Warnings are in place for Central and Northern Florida. 

Where is the heat dome headed next?

For the mid-Atlantic and Southeast, the heat relief won't arrive until Friday when a cold front will begin to slowly advance into the region, according to the FOX Forecast Center.

The cold front will not only bring cooler temperatures but an increased chance of rain.

This graphic shows the forecast heat indices through Wednesday, July 30, 2025. 

(FOX Weather)

However, relief is on the way. A strong cold front will break the heat Wednesday night, ushering in cool, dry air from Canada.

Places across the Midwest and Northeast could see a 20-degree drop in temperature by Thursday.

This graphic shows the forecast temperature swing across most of the northern U.S. this week.

(FOX Weather)