I’d expect the shortest day of the year to also be the coldest, with the coldest season of the year spreading out equally on both sides of it.
There are (at least) four different definitions of winter:
- Astronomical seasons are what you describe, and these are obviously based on astronomical events, for which the equinoxes and solstices are the perfect fix points. That the seasons start at these days is purely conventional, and in some times (roman empire) and places (Celtic calendar) people used these days as the center point of the season instead (also known as “Solar seasons”). Why those don’t match up with the actual temperature has already been explained in countless other replies.
- Meteorological seasons use a simple, month based approach, where winter is just December, January and February. That makes it easier for statistical usage but obviously is also just a man-made convention.
- The energy sector defines winter as the time of extended energy needs due to heating. Where I live, that’s defined as 1. of October - 31. of March, but for obvious reasons that’s highly dependent on where you are.
- Phenological seasons are a bit more what you’re looking for: They are based on biological events in indicator plants and a lot more complex than just being four fixed periods and only ever the same for small regions. Where I live, there are ten phenological seasons, winter starts when the English Oaks drop their leafs and ends with the blooming of the Common Hazle.
In other cultures there might be vastly different seasons. In many tropical countries you’ll only have the dry season and the monsun season.
To answer the original question, it’s because the earth is very large and retains the heat from warmer times preceding the solstice in the water bodies and the ground, like a buffer, so there is a lag time for things to lose that heat and get to the coldest air temps. As an analogy, if you heat up some rocks in the oven, then turn off the oven, the rocks will still stay hot for a long time and gradually cool off.
There are three popular reckonings for the 4 season model. The meteorological seasons, astronomical seasons, and solar seasons. The solar season places the solstices and equinoxes in the middle of each season. The meteorological seasons are based on temperature but these days are aligned with the months with summer/winter (depending on hemisphere) starting at the start of December and ending on the last day of February. The model the US uses is the astronomical model of seasons and makes the least sense to me, it places the start of each season on the solstices and equinoxes which means that midsummer is actually the start of summer there.
The model the US uses […] places the start of each season on the solstices and equinoxes which means that midsummer is actually the start of summer there.
We do meteorological here in Australia so December to February style. I had no idea there were places that put the equinox as the start.
That said, dividing the year into 4 seasons has always seemed very reductive to me. Our local indigenous aboriginals describe the weather in 6 seasons. People who have spent a life time observing the weather in the course of earning a living can describe what changes in patterns to expect from month to month. Of course, this knowledge is only applicable locally.
What do you mean when you say that the US uses this model and Australia uses that model? Who uses it and for what? In my country the government doesn’t tell us what season it is or what system to use. People just use whatever system they fancy and most likely it’s just based on gut feeling instead of a calendar day.
No one will look at you sceptically when you say “This is a cold winter” on a freezing November day, nor will the be confused if you say “What a nice spring day” on a sunny February afternoon.
People would 100% correct you if you use an alternative system.
I mean, obviously people would be confused if you called February “spring” in Australia, but then again you celebrate Christmas in summer 😁
which country do you live in? I live in Noongar country, they also use 6 seasons and I think it is a much better system. The Noongar seasons are an ecological system based on changes in nature
Yeah noongar.
We do meteorological here in Australia so December to February style.
I think they’re from Australia.
In Australia, the term “country” can also mean which Aboriginal land you’re on. Sort of equivalent to an American saying which Native American tribe’s “nation” they’re in, I think.
Reading again, that makes much more sense, thanks!
Yeah, it’s actually extremely common here in Australia. Major sporting events and other special occasions are often opened with a “welcome to Country” ceremony, performed by an Indigenous Elder.
Smaller events, from the weekly City Council meeting to radio programmes to some Australian Twitch streamers, will often include an “acknowledgement of Country” made by a non-Indigenous person. A simple statement like “I would like to acknowledge the Yuggera and Turrbal people who are the traditional custodians of the land on which we are gathered, and pay respects to their Elders past, present, and emerging.”
Keep an eye out, if you’re interested, for the opening ceremony of the Brisbane 2032 Olympics. Or any other sporting events that might come to your attention that are located in Australia.
That’s interesting, indeed! I’ll keep an eye out!
