WASHINGTON — While the temperatures may not reflect it just yet everywhere, fall is officially upon us. 

The autumnal equinox, occurring every September in the Northern Hemisphere, signifies the official astronomical beginning of fall. This year, the equinox falls on Monday, Sept. 22 at 2:19 p.m. Eastern.

Despite this, fall has already commenced for meteorologists. Unlike astronomical equinoxes and solstices, fall for meteorologists is based on annual temperature cycles and begins on the first of the month.

The first day of fall is on Monday, Sept. 22, 2025, in the Northern Hemisphere. 

These are just two different ways to carve up the year.

Meteorological seasons are governed by weather patterns. They divide the year into three-month periods according to annual temperature cycles. In this system, spring starts on March 1, summer on June 1, fall on Sept. 1, and winter on Dec. 1.

Astronomical seasons depend on how the Earth moves around the sun.

The onset of fall also indicates that the end of daylight saving time is approaching. Clocks will “fall back” one hour at 2 a.m. on Nov. 2, giving most people an additional hour of sleep. This change causes sunrises to occur earlier, with nightfall arriving before 7 p.m. We will not “spring ahead” until March 2026.

And speaking of upcoming calendar events: Monday marks just 94 days until Christmas and 66 days until Thanksgiving. 

As the Earth travels around the sun, it does so at an angle.

Throughout most of the year, the Earth’s axis tilts either toward or away from the sun, resulting in uneven distribution of the sun’s warmth and light on the northern and southern parts of the globe.

During the equinox, the Earth’s axis and its orbit line up so that both hemispheres get an equal amount of sunlight.

The term equinox is derived from two Latin words meaning equal and night. This reflects the fact that on the equinox, day and night are nearly the same length—although one might experience a few extra minutes, depending on your geographical location.

The Northern Hemisphere’s fall – or autumnal — equinox usually lands land between Sept. 21 and 24.

The solstices mark the times during the year when the Earth is at its most extreme tilt toward or away from the sun. This means the hemispheres are getting very different amounts of sunlight — and days and nights are at their most unequal.

During the Northern Hemisphere’s summer solstice, the upper half of the earth is tilted in toward the sun, creating the longest day and shortest night of the year. This solstice falls between June 20 and 22.

Meanwhile, at the winter solstice, the Northern Hemisphere is leaning away from the sun — leading to the shortest day and longest night of the year. The winter solstice falls between December 20 and 23.

Winter starts in the Northern Hemisphere with the winter solstice on Sunday, Dec. 21. The summer solstice is the longest day of the year, while the winter solstice is the shortest.