The first day of fall is the astronomical autumnal equinox. It is the day when the sun crosses the celestial equator moving southward. In 2025, the autumnal equinox will occur on Tuesday, September 23. In the Northern Hemisphere, this marks the first day of fall, while in the Southern Hemisphere, it marks the first day of spring.
The autumnal equinox is a significant day for many reasons. It is a time of change and transition, as the days begin to get shorter and the nights begin to get longer. The leaves on the trees start to change color and fall from the branches. The temperature also begins to cool down. For many people, the autumnal equinox is a time to reflect on the past year and to look forward to the year to come.
