The Official Start of Fall 2022 is Marked by the September Equinox

The Official Start of Fall 2022 is Marked by the September Equinox ...

The autumnal equinox occurs on September 22, marking the official beginning of Fall 2022.

The September equinox, which coincides with cooler temperatures and falling leaves, marks the official beginning of the fall season in the Northern Hemisphere. For the Southern Hemisphere, this year's autumnal equinox will take place on September 22 at 8:04 PM CDT.

According to Alphonse Sterling, an astrophysicist at NASA's Marshall Space Flight Center in Huntsville, Alabama, the Sun shines directly over the equator during an equinox, with the sun covering the entire day. Except for the North and South Pole, where the Sun almost straddles the horizon for the whole day, which are gradually shorter and darker. In the Southern Hemisphere, the days begin to last longer.

An illustration of the equinoxes of March (spring) and September (fall or autumn). During the equinoxes, both hemispheres receive roughly equal amounts of daylight (image not to scale.)

Seasons are the result of Earth's tilted axis, which always points in the same direction. As Earth orbits the Sun, the angle of sunlight that the Northern and Southern Hemispheres receive is different.

Mitzi Adams is an Assistant Manager in NASA's Marshall Space Flight Center's Heliophysics and Planetary Science Branch. "In the Southern Hemisphere, sunlight is less direct (winter), which means that the ground is not heated as easily."

A visual aid to better understand how the Earth's tilted axis influences the seasons throughout the year in the Northern and Southern Hemispheres. Credit: NASA/Space Place

While astronomical seasons are determined by the Earth's journey around the Sun, meteorological seasons are guided by annual temperature cycles. The seasons are divided into time periods that coincide with the weather and monthly calendar: December through February is winter, March through May is spring, June through August is summer, and September through November are autumn.

The equinoxes and solstices that occur twice a year are the other way around; they are the beginning of summer or winter. Solstices are the longest (summer solstice) day of the year.

The September equinox is a time when Earthlings are welcomed to a new season. After a long summer, those in the Northern Hemisphere should welcome early sunsets and late sunrises.

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