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Fall is here as of 4:44 p.m. Eastern Time on Sunday September 22, 2013.

Those Leaves Turned On Me! First Day of Fall, and There's a Nip in the Air

September 21, 2013

Goodbye, heat waves. Summer is finally over, at least up north, with the official, down-to-the-minute end coming at precisely 4:44 p.m. Eastern Time on Sunday September 22.

On this day, both day and night are approximately the same length, though now the days are shortening rather than lengthening, and a hint of chill is in the air. The actual occurrence, in the sky, is the moment that the sun crosses the plane of Mother Earth’s equator, known as the celestial equator, from north to south, explains.

Way up north the sun is teetering on the horizon as it prepares to depart for the winter.

Actually the days have been shortening all through the summer, but it has been all but imperceptible.

“The Autumnal Equinox marks the turning point, when darkness begins to win out over daylight,” the Farmers’ Almanac explains. “For the next three months, our hours of daylight will continue to grow shorter.”

The harvest moon has been shedding its light this week too, remaining in the sky all night and rising sooner than normal, right after sunset.

RELATED: That Big Pumpkin in the Sky: Harvest Moon Really Shines This Week

On this day, too, the sun rises due east and sets due west, as Sky and Telescope reports.

What all this means on the ground is a vibrant display of fall foliage, which this year will be most prominent in the mid-Atlantic states, reports In fact in some places the colors have not waited for September 22.

“Cold air and a dry August have prompted an early emergence of colors for parts of the area, including Pennsylvania, New York and New Jersey,” says. “Meanwhile, surrounding regions may be hindered by flooding rain and unseasonable temperatures.”

What happens over the next couple of weeks could determine the depth and breadth of the foliage season.

"Most important is really what happens at the end of September and beginning of October into the middle of October,” said Marc Abrams, professor of Forest Ecology and Physiology at Penn State University, to That's really the crucial period.”

Stay tuned—and start bundling up.