The late-season swelter will continue along much of the Atlantic Seaboard through the week as tens of millions head back to school and work.
The combination of temperature, humidity, sunshine, light winds and other factors will push AccuWeather RealFeel® temperatures from Atlanta and Savannah, Georgia, to Philadelphia and New York City past the 90-degree mark most days this week.
On occasion, RealFeel temperature will approach 100 F for a few hours during the late morning and afternoon in some cities.
Most nights will be uncomfortably warm and humid, especially in urban areas in the Interstate 95 corridor.
The conditions, more typical of mid-July, will cause difficulties for those with respiratory problems and those who do not have air conditioning.
Adding to the difficulties during a September heat wave, many public pools close for the season and some beaches no longer have lifeguards on duty after Labor Day.
Avoid strenuous activity during the late morning and afternoon hours, when the sun is the strongest and RealFeel temperatures are the highest. Avoid swimming at beaches where lifeguards are not on duty.
Temperature and humidity levels will fluctuate on a day-to-day basis in northern areas, but much less so near the coast and practically not at all in the South.
A bit of relief is forecast from the Great Lakes to part of the Northeast at midweek. A brief push of cooler, less humid air will expand into northern areas. Humidity levels may be shaved for a day or two in part of the mid-Atlantic. The relief will be preceded by showers and locally heavy, gusty thunderstorms.
According to AccuWeather Long Range Weather Expert Paul Pastelok, "The unseasonable warmth and high humidity will continue through Friday over much of the South."
Relief from Delmarva to the southern Appalachians will have to wait until later this coming weekend, when a stronger push of cooler and less humid air will arrive and will reach through the mid-Atlantic and part of the South.
"The very warm and humid conditions will expand northward again before the middle of the month," Pastelok said.
The end result will have more warm days, compared to cool days, compared to average for the first half of September.
"Near or just beyond the middle of the month, we expect a strong push of chilly air to expand southeastward from Canada," Pastelok said.
"It is possible the air mass at mid-month will be chilly enough for frost and perhaps an end to the growing season in parts of the Midwest and the interior Northeast."
In much of the South and the East, this Labor Day was the warmest of the unofficial summer holidays this year.