Uptick in humidity, thunderstorms forecast for Northeast Labor Day weekend
AccuWeather meteorologists say that Mother Nature will send a reminder during the upcoming holiday weekend that summer is not over yet, despite a brief fall-like pattern during the first couple days of September. The holiday weekend will not be without some wet weather, however, and some areas will receive much more rain than others.
"After a warmer-than-normal August for many places across the Northeast, September will begin on a seasonable note," said AccuWeather Meteorologist Andrew Kienzle.
The month of August came to a close with pleasant weather, including low humidity, and the weather through Friday in the region served as an early fall preview.
For those hoping for one last trip to the beach, lake or mountains, the unofficial end of summer will be just what warm-weather fans are hoping for. However, there will be weather complications in some locations.
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A warming trend got underway in the mid-Atlantic on Friday. Farther north, the early taste of fall continued in New England. It will take until the beginning of the Labor Day weekend for New England and upstate New York for temperatures to soar above normal. Meteorologists say Saturday will also mark an uptick in humidity levels.
Cities like Philadelphia and Washington, D.C. are forecast to have high temperatures around 90 degrees on Saturday, with dew points creeping up into the middle 60s. This will bring AccuWeather RealFeel® Temperatures into the mid-90s.
As the humidity increases, the added moisture will allow for the possibility of a spotty afternoon thunderstorm in western New York and northwestern Pennsylvania on Saturday. This will be the exception rather than the rule, and most places will begin the long weekend on a dry note.
Temperatures will continue their upward trend on Sunday, and even New England will become more humid by then. With normal high and low temperatures beginning to fall at a more rapid pace as September begins, some locations are forecast to be nearly 10 degrees above normal. In fact, it is not out of the question that a few spots approach records.
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"Some daily records could be challenged in places such as Philadelphia, where Sunday's forecast high of 91 degrees will approach the record of 93 degrees set in 2018," Kienzle said.
As the higher humidity levels settle over the region, there will also be an increase in showers and thunderstorms. A cold front will also enhance the coverage of storms, and one could occur almost anywhere in the region. The thunderstorms are not expected to turn severe over a broad area, AccuWeather forecasters say.
On Sunday, a zone of showers and thunderstorms will expand from the Ohio Valley to the central Appalachians and into the western part of New England.
"In this zone, the downpours may be frequent enough to spoil outdoor plans much of the day," AccuWeather Senior Meteorologist Alex Sosnowski said. "Even though much of the Northeast is in need of rain in terms of drought, downpours could lead to incidents of urban flooding."
The heat combined with the humidity will make AccuWeather RealFeel® Temperatures several degrees higher than what the thermometer reads.
The aforementioned front will slow down on Monday. Cooler and drier air will return to northern New England as high pressure noses in, but humidity will remain high elsewhere. Even where the humidity remains elevated, more clouds should keep temperatures at lower levels than on Sunday. With the front around, the thunderstorm risk will continue.
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"Rain and storms could impact most areas of the mid-Atlantic on Monday which could act to spoil some outdoor plans," cautioned Kienzle.
While not a widespread threat, places that receive the steadiest and heaviest rain may be at risk for localized flash flooding. This is especially true in hilly and mountainous regions, where runoff can more easily funnel into small streams and valleys.
Temperatures are forecast to stay near to above normal following the holiday weekend. New England should remain dry, but the mid-Atlantic will still have a chance of showers and thunderstorms. More substantial warmth may attempt to return northward again by the end of next week.
Since the storm and frontal system responsible for the showers and thunderstorms is likely to be slow-moving, the downpour risk is likely to extend into Tuesday as millions head back to work or school.
"The wet pattern could lead to more long-term drought relief in parts of the central Appalachians and New England," Sosnowski said.
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