A widespread, major heat wave will spread from the Midwest to the East and remain in place into the Fourth of July with both oppressive humidity and blistering highs that could flirt with some all-time records in parts of the mid-Atlantic states.

By late this week, over 175 million Americans in the Midwest and East will be at risk of either "major" or "extreme" heat-related health issues, according to the National Weather Service experimental HeatRisk product.

Triple-digit heat indices are expected for many, and daily low temperatures won't drop below the mid-80s for some, offering little relief at night.

(MAPS: 10-Day US forecast highs, lows)

Heat Alerts

The NWS has issued numerous extreme heat watches, warnings and advisories for the eastern half of the country this week, plotted in the map below.

These alerts stretch from the Central Plains through the Midwest, South and Northeast.

An extreme heat watch means dangerous heat is possible, while a warning means it's either happening now or imminent. Heat advisories are issued for heat that is less unusual, but could still be dangerous.

Northeast highlights

In much of the Northeast, the peak of this heat wave will be from Wednesday through at least part of the holiday weekend.

By Wednesday, highs at least in the mid-90s will be common from Virginia to parts of New England and upstate New York.

Parts of the I-95 corridor from southern New England to northern Virginia could reach triple-digit highs each afternoon from Thursday through Saturday.

This could flirt with all-time records in a few places, including both Philadelphia's record long streak of 100-degree-plus highs (3 straight days) and its all-time record high (106 degrees from Aug. 7, 1918). Daily record highs are expected, too.

It could also be the first triple-digit high in New York City's Central Park in almost 14 years (July 18, 2012) and the first back-to-back triple digit highs in Harrisburg, Pennsylvania, in 15 years (July 21-22, 2011).

Life-threatening heat indices will climb above 100 degrees in many areas and will likely top 110 degrees in the hottest parts of the mid-Atlantic states.

Washington, D.C., is going to flirt with the 100-degree mark three days in a row, which could break the record for consecutive days above that threshold for Dulles International Airport.

And overnight lows may struggle or even fail to drop below 80 degrees in the heart of Philly, Baltimore, New York, Boston and Washington, D.C., offering little nighttime relief, another life-threatening factor in heat waves.

All-time hottest daily low temperature records could also be tied or set in Philly (83 degrees) and New York's Central Park (84 degrees).

(MORE: Danger of nighttime heat)

Midwest highlights

The heat already intensified in the Plains and Midwest this past weekend and it is locking in place in the Great Lakes and Ohio Valley for much of this week.

In the Midwest, 90s will be common through much of this week, except in areas of the upper Midwest and Northern Plains where thunderstorms may provide some relief.

When you factor in the heat index, many across the Midwest will feel like the triple digits, making conditions outright dangerous to be exposed to for long periods. This includes places like Milwaukee, Chicago, St. Louis and Minneapolis. 

The best chance for daily record highs this week will be in parts of the Ohio Valley and southern Great Lakes, including Cleveland and Detroit. The Motor City could even flirt with a triple-digit high, something that hasn't happened at Detroit Metro Airport since July 17, 2012.

South

While the South is used to hot summers, the heat moving in will be both persistent and oppressive.

Much of the region had highs in the 90s last weekend, and that torrid heat will continue to linger through all of this week. Some locations could even top 100 degrees in both the Southern Plains and in the Southeast from Virginia into the Carolinas, where daily record highs are most likely.

Add in the southern humidity, and heat indices will be well over 100 from Texas to the Carolinas. 

Records that have fallen so far

Daily records for low temperatures have been the main area that records have broken or tied so far, which means little relief is expected in the overnight hours from this oppressive heat.

Rockford, Illinois, to the northwest of Chicago, only dropped to 75 degrees on June 29, which tied the daily record low set back in 1931.

Dallas saw their low drop to 81 degrees on June 29. That actually tied the previous record set back in 2024.

Scattered record lows were tied and broken across the Central Plains and the Southeast, and this list is going to grow each day this week.

How long will the heat last?

The heat will ease a bit over most of the Midwest by this weekend, where highs in the 90s may be limited to near the Ohio Valley.

There is also some relief for parts of New England and the interior Northeast by Sunday.

A little more heat relief may arrive for the mid-Atlantic states by next Monday or Tuesday, as the heat dome responsible for this heat wave may shift westward, bringing the majority of the above-average heat back to parts of the Plains and West.

(MORE: 5 things to know to stay safe in a heat wave)

Make sure you check back, as we will continue to update the forecast and keep a close eye on the holiday weekend. For a more detailed forecast for the Fourth of July, see our latest forecast article here.