Overnight temperatures will not drop below the mid to upper 70s. It's likely that other counties will be added to the list; an excessive heat watch, the step before a warning, has already been issued for much of Upstate.
Friday will be hot and very muggy with partly sunny skies and highs in the low 90s.
A bulging zone of high pressure known as a heat dome is responsible for these punishing temperatures, some 10 to 20 degrees above normal.
Reach out to neighbors who do not have air conditioning, or who spend much of their time alone.
More than 150 million people in almost 30 states were under a heat watch, warning or advisory on Thursday morning, according to CNN meteorologist Dave Hennen. By Saturday it will blanket much of the East Coast from Virginia up through New York City, where temperatures are expected to reach or be close to 100 degrees.
Anyone forced to work or be outside during the hottest part of the day should pay great attention to their bodies, and to take frequent breaks. Officials also are concerned about smog, which is exacerbated by the heat and makes it more hard for certain people to breathe, including the very young, the elderly and people with asthma or lung diseases.
The heat wave has prompted the city of Chicago to open cooling centers throughout the city for anyone looking for relief.
Never leave a person or pet in an unattended vehicle.
Dress in light-colored, loose-fitting clothing.
Consider whether you want to head outside: The National Weather Service recommends rescheduling strenuous outdoor activities to early morning or evening to avoid sun and heat exposure. Be sure to stay hydrated by drinking plenty of water. This heat dome is sprawled over the eastern half of the nation, resulting in oppressive heat and humidity from the Central Plains to the Northeast. "I keep lemonade and gallons of frozen water in the refrigerator".
Fullerton said this type of heat wave isn't unprecedented for the region, "you know, it's July, it's hot, it's humid, that's usually what happens around here". Anyone overcome by heat should be moved to a cool and shaded location.
Water is the safest liquid to drink during heat emergencies.