Astronomical versus Meteorological Fall

What’s the difference?

Did you know while late September is widely recognized as the beginning of Fall, some scientists start tracking the change of seasons beginning on September 1st?

Why the difference? Let me explain.

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Posted by Chief Meteorologist McCall Vrydaghs on Wednesday, September 1, 2021

Meteorological vs. Astronomical Seasons

Meteorologists and climatologists define seasons based on the annual temperature cycle, while astronomers define seasons based upon the position of Earth in relation to the sun.

Meteorological seasons are grouped into three-month cycles to help collect and keep better data. The first day of meteorological fall begins on September 1st and will last through November 30th.

Astronomical fall will begin Wednesday, September 22nd at 3:21 p.m., the exact moment the sun passes over the equator from north to south.

Just like during the spring equinox, this is one of two days of the year with nearly 12 hours of daylight and 12 hours of darkness. The difference is from this date on, days will slowly become shorter and nights will be longer until the winter solstice occurs on December 21st.

Daylight Saving Time

Of course, with the changing of seasons comes less daylight, but there is something else in play that will cause our sunsets to happen earlier.

wo months Daylight Saving Time will come to an end. It’s an annual tradition when Americans set their clocks back one hour. This changing of time will happen on Sunday, November 7th at 2 a.m.

In case you’re wondering, the sunset for Dayton on November will be at 5:27 p.m.

The tradition of setting our clocks ahead one hour during the summer months then back an hour during the winter was created to make better use of daylight hours.

Looking Ahead

Due to the decrease in daylight hours and sun angle, temperatures will steadily fall through the next couple of months. On average, the daily high will fall from the lower 80s this week, to the middle 30s by the first day of winter.