Astronomically, fall usually starts on the date of the autumnal equinox, which most often falls on September 22 or 23 in the Northern Hemisphere, but can occasionally be on September 21 or 24.

Quick Scoop: What “when did fall start” means

There are actually two common answers people use when they talk about when fall starts:

  1. Astronomical fall
    • Starts on the autumnal equinox.
    • This is when day and night are roughly equal in length.
    • In practice, this usually lands on September 22 or 23 each year in the Northern Hemisphere, with rare years where it falls on September 21 or 24.
  1. Meteorological fall
    • Defined by calendar months rather than the equinox.
    • Runs from September 1 to November 30 in the Northern Hemisphere.
 * Used by many weather and climate agencies because it makes statistics and comparisons easier.

So if you’re asking “when did fall start” in a general, seasonal sense, many people would say September 1 (meteorological). If you mean the “official” astronomical start, it’s the date of the autumnal equinox , usually around September 22–23.

Different ways people answer this

People and sources often treat the start of fall differently:

  • Some go by feel : it’s fall when it cools down, leaves change, and school is back in session (often just after Labor Day in early September).
  • Governments and climate services often use meteorological fall : September 1–November 30.
  • Many calendars and almanacs highlight astronomical fall : starting on the equinox, which is considered the “official” seasonal change in a lot of popular references.

If you tell me which year (and which country/hemisphere) you care about, I can give you the exact equinox date for that specific fall season.