Weather 101: Meteorological versus astronomical seasons

As if a recent spell of fall-like weather hasn’t given us a clue yet, the Valley has just gone through another sign of fall’s arrival.

Yesterday, September 1st, marked the first day of the three-month meteorological fall season. The season, stretching through September, October, and November, is one of three major ways we divide our calendar into seasons. While weather nerds may be switching seasons now, the majority of folks still consider it to be the summer, which will end in three weeks. How do meteorological seasons compare with astronomical seasons, which have been the tradition?

Earth rotates, orbits, and tilts to show the sun in different ways. Tilt, like using your body to lean forward and backward, is the way we get astronomical seasons and different sun angles in the sky. Our planet tilts on a yearly scale. When it “leans” into the Sun from the Northern Hemisphere, we call that summer. When it “leans” away from the sun, we call that winter. It is important to note that both sides of the Earth experience different seasons at different times. 

For example, the summer solstice occurs at the time when the Northern Hemisphere is at its maximum "lean" into the Sun. During the fall or spring equinoxes, Earth has zero tilt, as if someone were standing straight towards the sky. This year, the autumnal equinox will occur on September 22nd, though the date and time can vary by about a day or two each year.

Meteorological seasons emulate the same feel, while also attempting for more consistency throughout the year. Meteorological winter spans between December, January, and February. March kicks off spring, going through April and May, as well. Summer starts on the first day of June and ends on August 31st. September, October, and November, featuring a decline in temperatures, headline the final season of the year. These three-month periods roughly align with how temperatures cycle, where summer and winter represent the “peaks” of the yearly cycle, while fall and spring are “transition seasons” with a large swing in temperature. 

It can be argued that meteorological seasons “fit the bill” for season’s definitions better. Mid-March, whose average temperatures here in Youngstown are in the mid-40s with a stronger sun angle, is classified as spring within meteorological definitions rather than winter, traditionally. 

Because of the meteorological season’s consistent framework of three-month blocs, tracking and analyzing climate statistics for forecasting, agriculture, and commerce can flow much more easily. This makes seasonal analysis easier for those not just on the TV screen, but also for meteorologists who make important climatological decisions.

Here's the full difference in dates between meteorological and astronomical seasons: