The official start to the fall season, the autumnal equinox, occurs on Sunday, Sept. 22. What exactly happens during the equinox? Here’s a breakdown: According to NOAA, an equinox occurs when the Earth’s axis is tilted neither away nor toward the sun.

On Sept. 22, the fall equinox formally heralds in autumn and marks the end of summer in the Northern Hemisphere.

This year, the fall equinox and Libra season will be particularly intense and transformative, because each zodiac sign’s horoscope will be affected by the current astrology in an even more significant way than usual.