What determines the first day of fall?
The autumnal equinox, usually occurring on September 22 or 23, means fall is officially here. The autumnal equinox is one of only two days—the other is the spring, or vernal, equinox—when the Sun is directly above the Equator, ostensibly dividing night and day into equal portions.
The autumnal equinox, usually occurring on September 22 or 23, means fall is officially here. The autumnal equinox is one of only two days—the other is the spring, or vernal, equinox—when the Sun is directly above the Equator, ostensibly dividing night and day into equal portions.