Autumnal Equinox: The First Day of Fall is September 22

September 20,2014

 
With leaves changing, baseball's regular season coming to an end and college and NFL football beginning, you know that summer's last fling is upon us. Goodbye to the smell of sunscreen and hello hot apple cider and pumpkin pie.
Meteorologically speaking, autumn began on Sept., 1 but the autumnal equinox marks the astronomical start to the fall season.
This year, the baton is passed from summer to fall (in the Northern Hemisphere) on Monday, Sept. 22, at 10:29 p.m. EDT.
So what exactly happens during this time?
Twice a year, around March 20 or 21 and Sept. 22 or 23, the sun's rays shine directly over the Earth's equator. These two days are known as the March (vernal or spring in the Northern Hemisphere) equinox and the September (autumnal) equinox.
The specific time of 10:29 p.m. EDT marks the passage of direct sunlight over the equator from the Northern Hemisphere to the Southern Hemisphere.

Nearly Equal Daylight

During both the vernal and autumnal equinox, day and night are balanced to nearly 12 hours each all over the world.
Instead of a tilt away from or toward the sun, the Earth's axis of rotation is perpendicular to the line connecting the centers of the Earth and the sun during an equinox.
From this point on, daylight in the Northern Hemisphere will gradually grow shorter until the winter solstice, which occurs on Dec. 21, 2014. The opposite occurs in the Southern Hemisphere, where daylight will now grow longer.