Autumnal Equinox 2026 Marks Start of Fall in Northern Hemisphere on September 23
The autumnal equinox in 2026 will occur on Wednesday, September 23, at 00:05 UTC. This astronomical event signifies the official start of autumn in the Northern Hemisphere and spring in the Southern Hemisphere. The equinox is a precise global moment when the sun crosses the celestial equator, moving from north to south. Due to Earth's axial tilt and its orbit around the sun, this crossing results in gradually shorter daylight hours and cooler temperatures in the Northern Hemisphere. While the term 'equinox' literally means 'equal night,' atmospheric refraction and the method of measuring sunrise and sunset mean that most locations experience slightly more daylight than darkness on this day. The exact calendar date of the equinox can vary between September 21, 22, 23, or occasionally 24, depending on the year and time zone. 
