The calendar will flip to October this week, but instead of bundling up in sweaters and boots, people in the Northeast will be dressing for heat more typical of mid-summer.
AccuWeather meteorologists say it's still too early to remove air conditioning units as heat will build this week in what may be summer's last gasp.
The hot air that has been baking the Southern states for weeks will surge northeastward into Wednesday, bringing a resurgence of high temperatures in the 80s and 90s F. Such temperatures are 10-20 degrees Fahrenheit above the rapidly falling normal highs at this point in the year.
An uptick in humidity will send AccuWeather RealFeel® Temperatures several degrees above these marks.
The heat will first surged into the Ohio Valley on Monday. However, after a murky start, warmth busted loose over much of the mid-Atlantic on Tuesday afternoon.. Wednesday is likely to be the hottest day of the warm surge for some Interstate 95 cities.
"Record highs will be in jeopardy for many areas," AccuWeather Meteorologist Tyler Roys said, adding that hundreds of record highs may be challenged this week.
Indianapolis; Cincinnati and Cleveland, Ohio; Pittsburgh, Philadelphia and Harrisburg, Pennsylvania; Charleston, West Virginia; New York City; Baltimore; and Washington, D.C., are just a few of the places where new record highs may be stamped in the history books during the first half of this week.
A strong temperature contrast will set up across the region. For example, on Wednesday, temperatures may be no better than 50 over northern New England, while highs in the 90s are forecast for part of the mid-Atlantic region.
A high of 90 degrees Fahrenheit is forecast for New York City's Central Park on Wednesday. If the mercury reaches that mark, it would tie the record high for the date previously set in 1927. Forecasters say the last time the city had a high of 90 or greater in the month of October was Oct. 6, 1941.
"It may be a close call between record warmth and approaching chilly air from the north around New York City, as well as northern Pennsylvania, northern New Jersey and southern New England," according to AccuWeather Senior Meteorologist Alex Sosnowski.
"A back-door cool front will attempt to push southward on Wednesday, stall Wednesday night, then lift northward briefly on Thursday," Sosnowski said.
Indianapolis and Pittsburgh are two cities where records from the late 1800s could be rewritten.
Schools that lack air conditioning may dismiss early during the summery surge.
Residents are reminded to take the necessary precautions in the heat to lessen the risk of heat-related illnesses. These include limiting strenuous outdoor activities during the peak heating of the day, drinking plenty of water and wearing light-colored, loose-fitting clothing.
Never leave pets or children in a sealed vehicle for even a short amount of time.
The warmup will be limited across northern New York and central and northern New England Tuesday into Wednesday with periods of rain and thunder expected, according to Roys.
Some of this rain will eventually reach the mid-Atlantic late in the week, with a dramatic shift in the weather pattern expected to follow.
"Big changes are on tap for the end of the week as a strong cold front gradually pushes through the mid-Atlantic and ushers in a true taste of fall," AccuWeather Meteorologist Kyle Elliott said.
This cold front is expected to bring an end to the seemingly endless summer that the Northeast experienced through the month of September.
"High temperatures on Friday may be confined to the 50s across New England and the low to mid-70s farther south," Elliott said.
There is the potential for a widespread frost to occur over interior areas as the chilly air settles in by the first weekend of October.
"In some places, on one hand, while the growing season may come to an end with the arrival of the chilly air, on the other hand, it may mark the end of the allergy and mosquito season," Sosnowski said.
The crisp air and return of sunshine on Saturday is likely to create ideal conditions for favorite fall activities, such as college football games, pumpkin and apple picking and leaf peeping.