01:09 Chilly Temperatures to Start October Over Much of the Country The eastern two-thirds of the country will see fall-like temperatures next week.

At a Glance Torrid heat and humidity will linger in the East this weekend.

The heat index will rise to dangerous levels in parts of those regions.

This level of heat could become deadly, especially in large metro areas.

Widespread daily record highs are unlikely, but a few will be set, particularly in the Northeast

Relief from the intense heat will arrive in the week ahead. A heat wave will linger in the East and parts of the Midwest this weekend, bringing many cities their hottest temperatures so far this summer and creating dangerous heat indices.

The National Weather Service has issued excessive heat warnings and heat advisories in the Plains, Midwest and much of the East to warn residents of the dangerously hot conditions.

Excessive heat warnings are issued when afternoon heat indices are expected to be dangerous, if not deadly, for those with prolonged exposure to the heat. Overnight temperatures may not drop far enough to bring relief from the heat, particularly in larger cities, which tend to "hold in" heat more than rural areas.

(MORE: What Is the Heat Index and Why Is it Used?)

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/staticmaps/DCT_SPECIAL27_1280x720.jpg" srcset="https://s.w-x.co/staticmaps/DCT_SPECIAL27_1280x720.jpg 400w, https://s.w-x.co/staticmaps/DCT_SPECIAL27_1280x720.jpg 800w" > Heat Alerts (From the National Weather Service.)

Temperatures ranging from the mid-90s to near 100 degrees are likely to linger in parts of the central and eastern states this weekend.

When combined with dew points into the 70s, this will produce heat indices well over 100 degrees – a combination of heat and humidity that could be dangerous for those spending too much time outdoors. A few spots, like Washington, D.C., may see heat indices over 110 degrees this weekend.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/staticmaps/DCT_SPECIAL22_1280x720.jpg" srcset="https://s.w-x.co/staticmaps/DCT_SPECIAL22_1280x720.jpg 400w, https://s.w-x.co/staticmaps/DCT_SPECIAL22_1280x720.jpg 800w" > Forecast Heat Index

Friday, heat indices of 110 degrees or higher were widespread in the mid-Atlantic states, Great Lakes, upper Midwest, Plains and South. At least a couple locations even registered 120 degree-plus heat indices in the upper Midwest.

Several cities are likely to see their hottest temperatures so far this summer, including Detroit, New York City and Washington, D.C.

(NEWS: Latest Heat Wave Impacts)

We're not forecasting widespread record-high temperatures. Since we're in what is typically the hottest time of the year , the benchmarks for setting heat records are very high.

Saturday will have the best shot at setting several record highs in the Northeast, but a few may also fall into Sunday.

Records fell on Saturday in New York City (JFK - 99 degrees) and Atlantic City, New Jersey (99 degrees).

Hartford and Philadelphia may flirt with their first official 100-degree temperatures since July 2012 this weekend. Washington, D.C., may also hit the century mark for the first time since August 2016.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/staticmaps/DCT_SPECIAL38_1280x720.jpg" srcset="https://s.w-x.co/staticmaps/DCT_SPECIAL38_1280x720.jpg 400w, https://s.w-x.co/staticmaps/DCT_SPECIAL38_1280x720.jpg 800w" > Forecast Highs

Evening and nighttime temperatures won't be very cool, with lows in the mid- or upper 70s common in larger cities from the Midwest to the East.

(MAPS: 10-Day U.S. Forecast Highs/Lows)

Friday, both Chicago and Rockford , Illinois, failed to dip below 80 degrees, tying Rockford's all-time hottest daily low temperature, set over 100 years ago.

These stuffy overnight low temperatures are expected to set dozens of daily record-warm lows through Sunday morning in a number of cities, according to the National Weather Service.

Extreme heat claimed 108 lives in the U.S. in 2018 , more than any other weather phenomenon, including hurricanes Florence and Michael, tornadoes, flooding or lightning.

(MORE: Why Nighttime Temperatures are Also Dangerous During Heat Waves )

Reduce your time outdoors during the hottest time of day, stay hydrated and check on a friend, relative or neighbor who may not have air conditioning.

Cooler Temperatures Arrive in the Upcoming Days

The good news is that this heat wave will abate soon as the weather pattern reconfigures itself once again.

A southward plunge of the jet stream is now spreading southward to the East Coast. This will usher in cooler, drier air to much of the Plains, Midwest and East, dropping temperatures near or even below average for late July. This could mean highs in the low- to mid-80s across those regions, with temperatures dropping into the 60s or lower overnight.

For more on this pattern change and what it could mean for you, please read our forecast article on that .