Quaking Aspen (Populus tremuloides) shown here in the Valles Caldera, receives its namesake from the way its leaves seem to ‘quake’ in even the barest of breezes. Courtesy/VCNP
Today marks the first day of fall and the autumnal equinox
During the autumnal equinox, day and night are balanced to about 12 hours each all over the world. Instead of the Earth tilting away from or toward the sun, its axis of rotation becomes perpendicular to the line connecting the centers of the Earth and the sun.
“This change in the tilt causes the change in seasons with the northern hemisphere moving from the warmth of summer to the chill of winter,” said weather.com digital meteorologist Linda Lam. “This process includes a shift in the overall location of the jet stream which plays an important role in weather conditions.”
From that point on, daylight in the Northern Hemisphere gradually becomes shorter up until the winter solstice. This is the opposite of what occurs in the Southern Hemisphere, where daylight won’t grow any longer.
Fall is the transition between when the sun’s equator lines up with the Northern Hemisphere in the summer and the Southern Hemisphere in the winter.
In addition to seeing the leaves change and advertisements for pumpkin spice-flavored everything, the equinox brings about temperature changes.
“Fall is a transition season and in the U.S. fall is usually characterized by large variations in temperatures, as well as an increase in low-pressure systems bringing rain, storms and even snow across the country,” Lam said. “Generally in the U.S. after the fall equinox, temperatures continue to become colder and snow becomes more common.”
Today’s Equinox Times:
- Eastern Daylight Time: 10:21 a.m.
- Central Daylight Time: 9:21 a.m.
- Mountain Daylight Time: 8:21 a.m.
- Pacific Daylight Time: 7:21 a.m.