Meteorological vs. astronomical Fall: when does Autumn actually start?

September first marks the start of fall for meteorologists.

However, many know the start of fall is marked by the autumnal equinox later in the month around September 22.

The main reason for the difference in dates comes down to math.

For meteorologists, a relatively unchanging date makes calculations for seasonal averages easier.

Most meteorological seasons last around 90-92 days depending on a leap year, providing far more consistency between seasons that helps validates forecasts and outlooks.

For meteorologists, Fall goes from September 1- November 30.

None of this is to say that one start date for the season is necessarily "better" than the other, just that the two are grounded based off different reasons.

Over 57% of meteorological Fall seasons since 1991 have seen at least one day of 90F or higher, with our most recent day being back in 2021.

Michiana will likely see the first day of 90F weather this weekend, although our highest temperature in the 90s will be Monday.

The warmest day Michiana has seen in the Fall was 99F in 1908.

Moving away from the heat, Fall in Michiana means we usually see our first frost by October 7. Last year, our first frost was on October 4.