Northeast, Upper Midwest to feel more like September this weekend

By Alex Sosnowski, AccuWeather senior meteorologist

Much to the delight of fall weather fans, temperatures and humidity levels over much of the Upper Midwest and Northeast will be more typical of September, rather than the middle of August, through Sunday.

Many people will be able to open their windows to cool the house at night, instead of running the air conditioner or fan. Energy demands will ease.

Despite the cooler conditions, the weather will still be plenty warm enough for outdoor plans, including swimming.

People who have been avoiding the heat of the summer for outdoor projects may be able to accomplish their tasks this weekend.

While the August sun will still make for warm afternoons, the weather pattern will bring a break from muggy nights and humid days.

Highs are forecast to range from the upper 70s to near 80 F over the northern tier to the upper 80s around the Chesapeake Bay.

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The air hanging around this weekend had its origins from northern and central Canada and will reveal its identity at night in the form of cool conditions.

Low temperatures in the Northeast are forecast to range from the middle 40s over the mountains of northern New England to the upper 60s around the Chesapeake Bay.

Meanwhile, at their lowest point, nighttime temperatures over the Midwest are expected to range from the lower 50s over the Upper Peninsula of Michigan and northern Minnesota to the middle 60s along the Ohio River in Illinois, Indiana and Ohio.

Despite the coolness, few, if any, records are expected to be broken. For example, record lows in Bradford, Pennsylvania, this weekend are in the upper 30s to near 40.

Along with the feel of early autumn this weekend will be the likelihood of areas of fog during the early-morning hours.

"Light winds and a mainly clear sky will lead to ideal conditions for the formation of fog, especially in the river valleys of New England and the central Appalachians this weekend," according to AccuWeather Meteorologist Brett Rossio.

While some warmer and more humid air will begin to filter in from the west and south over the Midwest later this weekend, the transition is not likely to begin in the Northeast until early next week.

The leading edge of more humid air will be marked by clouds, showers and thunderstorms across parts of the Upper Midwest from Saturday night to Sunday.

"There is a slight chance rain falls for part of the day on Sunday at Michigan International Speedway," Rossio said.

"The area may be near the northern edge of a complex of thunderstorms passing by to the south for a time. But even if [it] did rain, the feature may depart by the afternoon in time for the Consumers Energy 400 NASCAR race."

While warmer weather will gradually move in next week, it may take until a storm moves eastward with rain to the north and thunderstorms to the south to move by before the larger transition occurs later in the week.

That storm is likely to delay the warmup by a few days.

Cooler-than-average conditions are likely north of the storm trackwhere it rains for a day. Temperatures south of the steady rain area are likely to be near average.

Normal highs during the third week of August range from the upper 70s across the northern tier to the middle 80s over the Ohio Valley and the upper 80s in southeastern Virginia.

A period of above-average warmth seems likely the following week for a large part of the Midwest and Northeast.

Download the free AccuWeather app for the latest temperature forecast for your area. Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.