when was the last day of summer

The most recent “last day of summer” depends on which definition you care about:

• Astronomical summer (Northern Hemisphere):
  The last day of summer was September 22, 2025 , which is when the autumnal equinox arrived and fall officially began.

• Meteorological summer:
  If you go by the meteorological definition (used by weather services: June, July, August), the last day of summer was August 31, 2025.

In everyday U.S. culture, many people also treat Labor Day (September 1, 2025) as the “unofficial” last day of summer, since it caps off the traditional vacation season.

So if someone asks “when was the last day of summer,” the precise, science- based answer is September 22, 2025 (astronomical), but socially and weather‑wise, people might mean August 31, 2025 or Labor Day.