The official first day of fall (in the Northern Hemisphere) is the autumnal equinox , which falls each year between September 21 and 24 , most often on September 22 or 23.

What “official” means here

Astronomically, fall starts at the moment the Sun crosses the celestial equator heading south, called the autumnal equinox. That instant is what most calendars, observatories, and national weather services use as the official start of fall.

Meteorologists sometimes define a different, simpler system:

  • Meteorological fall = September 1 to November 30 in the Northern Hemisphere.
  • This makes record-keeping and climate statistics easier, but it’s not the astronomical “official” start.

Typical dates (Northern Hemisphere)

The astronomical first day of fall usually lands on:

  • September 22 or September 23 most years
  • Occasionally September 21 or 24 in some time zones, due to leap years and Earth’s orbit.

For example:

  • 2025: September 22
  • 2026: September 23

Quick table of example years (astronomical fall, Northern Hemisphere)

[3][1] [1][3] [7][3][1] [5][9][3][7][1]
YearOfficial first day of fallDay of week
2023September 23Saturday
2024September 22Sunday
2025September 22Monday
2026September 23Wednesday

Why people say “September 1 is fall”

Online and in forums, many people jokingly or personally treat September 1 as “the first day of fall” because:

  • Weather often feels more autumn-like starting early September in many regions.
  • Stores roll out fall decor, Halloween items, and pumpkin-flavored everything by late August or early September.
  • Meteorological seasons use September 1 as the start, which influences media and public perception.

So you’ll see posts like:

“It’s September 1st, which means it’s the first day of fall… right?”

They’re not wrong in the meteorological or “vibes-based” sense, but astronomically the official first day is still the equinox. TL;DR:

  • Official (astronomical) first day of fall: autumnal equinox , usually September 22 or 23 in the Northern Hemisphere.
  • Meteorological fall: September 1. Many people and online communities use this as their “practical” first day of fall.

Information gathered from public forums or data available on the internet and portrayed here.