When Does Fall Season Start: Meteorological vs. Astronomical

MADISON, Wis. (CIVIC MEDIA) – It all depends on how you measure it, differences scientifically explained.

It’s fall, ya’ll! Sweater weather is upon us. The beginning of the autumn season marks the end of warm summer days and the start of longer chilly nights.

So what is the difference between the two dates that are set  3 weeks apart? Which one is right and which one do you follow? 

Well most people flip the page to the Fall season according to the astronomical, the fall equinox. Which officially takes place on September 22nd of this year. It’s based on how Earth moves around the sun. On that specific day, it’s placed precisely where the length of daytime and nighttime are exactly equal.

But since this shifts so much from year to year scientists need to keep things consistent for climate record keeping.

The Meteorological fall already started on Sunday, September 1st. You know, when the first blast of cooler air filtered in, and now we are in the thick of our second snap. Civic Media’s Meteorologist Brittney Merlot says, “We group the season of Fall into three months, the BERRRRRR months of September, October and November.” 

It’s defined by the weather based on annual temperature cycles. It’s easier for keeping stats as it follows the calendar. Making data more accurate and useful for agriculture and commerce. 

In the world of Meteorologists, Winter begins on a different date too, December 1st. While the astronomical change occurs on December 21st, on the shortest day and longest night of the year. 

So really you’re not wrong on whichever day you choose to celebrate it. Or for some, like Meteorologist Brittney Merlot, maybe it’s both! 

But there is a set date where we can all see the “Harvest Moon”. Which is the full moon closest to the flip to Fall. The name dates back to a time before electricity when farmers depended on the moon’s light to harvest their crops late into the evening.

This year’s harvest moon is the last supermoon of the year too. Which means it’ll move closer to Earth and appear larger. It’ll emerge on a Monday and will reach peak illumination at 9:30 at night on Tuesday, September 17th.