Will cooler air early this week signal the end of summer heat in northeastern US?

Jordan Root, Meteorologist for AccuWeather.com

AccuWeather reports following a week of record-breaking heat, some northeastern U.S. cities will find the opportunity to turn the air conditioners off and pull out the sweatshirts as cooler air settles in for a few days.

A strong cold front that moved across the Great Lakes and Northeast on Sunday is responsible for sending a much cooler air mass into the region. High temperatures into Tuesday will be cut 5 to 15 degrees Fahrenheit compared to highs this past week.

"From New York City to Washington, D.C., highs in the 90s will be replaced with highs in the upper 70s to middle 80s early in the week," AccuWeather Meteorologist Renee Duff said.

The recent heat broke records on Friday in several cities including Philadelphia, Boston, Providence, R.I., and Trenton, N.J. among others.

Philadelphia also set a new record for the highest overnight low temperature on Saturday morning. The temperature dropped to 80 F, making it the highest low for the month of September on record.

While the air will feel cooler as compared to past days, temperatures will actually be around normal for this time of the year.

Perhaps the most noticeable aspect of this airmass will be the drop in humidity. Steamy, July-like air brought very uncomfortable conditions to the Northeast over the past few days.

Dew points, a variable used to determine how much moisture is in the air, have dropped from the 70s to the upper 40s and lower 50s, resulting in a change from oppressive to much more pleasant conditions.

High pressure will follow the front and remain positioned across the Northeast through Tuesday. This will help keep sunshine and dry conditions around for a while.

"The weather will give residents an excellent opportunity to take part in outdoor activities," Duff said.

Cooler and less humid days will lead to chilly nights across the Northeast, especially in some of the lower spots across the Appalachians where temperatures will dip into the 40s.

Areas closer to the Interstate 95 corridor and the coast will feel temperatures drop into the 50s and lower 60s.

Did we experiences summer's last gasp this past week?

While astronomical autumn does not begin until Sept. 22, meteorological autumn began on Sept. 1, denoting a season change from the year's warmest months to a season where the temperature is rapidly declining.

"This past weekend was likely the last of the true summerlike heat and humidity, but temperatures will largely remain above normal for the remainder of September," AccuWeather Long-Range Meteorologist Ed Vallee said.

A brief surge of warmth is expected towards the middle of this week as a southerly flow returns to the Northeast. Temperatures will return to the upper 80s and lower to middle 90s for the Interstate 95 corridor while upper 70s will be found farther west.

However, just as quickly as temperatures rise, another cooldown is set to arrive toward the end of the week.

"Cold fronts will become more common across the Northeast through the rest of September," Vallee said.

This roller coaster-type weather pattern is typical for autumn months and will only increase in frequency and magnitude through November.

"This will lead to a few warm and muggy days, but these will be relieved by cooler, more fall-like days," Vallee said. "Overall though, we expect warmer temperatures to win out over the lower temperatures through the rest of the month."