Every year on February 2nd, the people of Punxsutawney, PA dress up like it’s 1886, pull a groundhog named Phil out of a box and ask him when winter will end. Not surprisingly, meteorologically-inclined marmots are not reliable predictors of spring.
But why divide the year into seasons in the first place? The word seasonal was born on the farm, since for a long time surviving another trip around the sun meant knowing when to sow your seeds. In most our minds, winter is when it’s coldest, summer is when it’s hottest, and spring and autumn happen in between.
You probably figured that much out before kindergarten. But those aren’t the seasons on your calendar. In most of the northern hemisphere, especially in the U.S., the coldest quarter of the year begins several weeks before the official start of winter, and summer leaves out a good chunk of warm weather.
How did our seasons get so detached from our seasons? Because Earth’s axis points alternately toward and away from the sun, we know there’s less daylight in winter. and more daylight in summer. So shouldn’t winter be the darkest time of year, and summer the time with most daylight? If we did that, then the solstices should fall at the midway point.
Several cultures define their seasons exactly this way, and it might sound familiar from a certain William Shakespeare play where the summer solstice falls at amid summer. But like a big brisket, Earth cools and heats very slowly, and it takes time for changing solar energy to move the thermometer.
Water absorbs even more heat than land, so places near oceans and lakes experience greater lags between more solar energy and warmer weather. The opposite happens in winter, all that water stores heat and keeps things from getting cold as soon as the sun starts to fade.
The start of cold or hot periods gets shifted towards the solstices, but in most places they *still* don’t line up with the coldest and warmest quarters. It probably won’t surprise you to learn that a lot of our modern four-season system traces its origins to the Romans.
Because so much of their territory was insulated by large bodies of water, the temperatures they experienced lined up neatly with the solstices, which were pretty big deal to ancient astronomers and festival-lovers. This system was applied to a whole hemisphere, even though it didn’t make sense in a lot of places.
If anyone can mess up a calendar, it’s the Romans! Numa! Depending on whether you care more about astronomy or temperature, there’s a lot of different ways to define seasons, and none of them are perfect. Of course, most other living creatures don’t worry about any of this stuff, they just follow Earth’s natural climate cycles where they live.
Several indigenous Australian cultures define their seasons just this way, starting new seasons based on what plants and animals are around at any time. They’d probably think Groundhog Day makes a lot of sense. Stay curious.