The first day of autumn in Australia is 1 March each year by the standard meteorological (calendar) seasons used across the country.

In Australia, seasons are usually defined in three‑month blocks:

  • Autumn: 1 March to 31 May.
  • Winter: 1 June to 31 August.
  • Spring: 1 September to 30 November.
  • Summer: 1 December to 28/29 February.

Astronomically, some sources also note the autumn equinox (around 20 March in 2026) as the official start of autumn in the Southern Hemisphere, but everyday usage, weather services, and calendars in Australia treat 1 March as the first day of autumn.