The temperatures outside are starting to feel like fall, but fall doesn’t arrive until late September,
right? Stop! Wait! Not in the eyes of meteorologists. When most people think about the first day
of summer, fall, winter, or spring, they usually go straight to the calendar dates we’ve all grown
up with.
Summer starts on June 20 or 21, fall begins on Sept. 22 or 23, and winter kicks in on
Dec. 21 or 22, and spring arrives March 19 or 20. Those dates are what we call the
astronomical seasons — they’re based on the position of the Earth in relation to the sun. The tilt
of the Earth’s axis and our orbit create solstices and equinoxes, marking the “official” change of
the seasons.
But here’s where meteorologists do things a little differently. We don’t sit around waiting for the
sun to hit just the right angle. Instead, we divide the year into four equal chunks of three months
each, based on annual temperature cycles. These are called meteorological seasons. For us,
spring always runs from March 1 through May 31, summer from June 1 through Aug. 31, fall
from Sept. 1 through Nov. 30, and winter from Dec 1 through Feb. 28 (or
29 if it’s a leap year).
Why do we do it this way? Well, for one, it makes weather records and climate statistics much
cleaner. If you’ve ever tried to track average rainfall or compare the hottest summers on record,
Meteorological seasons also line up much more closely with what we actually experience. Think
about it: in Perryville, by the time March 20 rolls around, spring is already in full swing. We’ve
often had thunderstorms, early warm-ups, and even budding trees. Waiting another three weeks
for an “official” start just doesn’t make much sense when the weather has already turned the
page. The same goes for winter — December is usually cold, sometimes snowy, and undeniably
winter-like. But under the astronomical calendar, winter doesn’t officially start until just a few
days before Christmas.
So, while both calendars are correct, meteorologists prefer the version that fits the reality of our
climate and helps us measure weather in neat, even blocks of time. Astronomical seasons are tied
to the heavens. Meteorological seasons are tied to the weather we live in every day.
From my window, that just feels like the better way to keep track of the seasons. And as
Perryville wakes up to crisp mornings in the weeks ahead, folks may find themselves reaching
for a light jacket, even though the calendar says “summer.” In the eyes of a meteorologist, fall
will already have arrived.
