Danger! Human stuff! Remember my disclaimer! Don't fall for the naturalistic fallacy!
It shouldn't come as a controversial that our behaviour is different in winter. We sleep more, we're less energetic, we've got slightly larger appetites, etc. Previous studies had shown that humans also experience shifts in hormone levels. Do seasonal fluctuations in men's hormone correspond to changes in mate choice?
Two Polish researchers, a place with something that passes for a proper winter, decided to put this question to the test. They showed over a hundred men of varying backgrounds computer-generated pictures of females of varying attractiveness, and had the respondents record scores for various attributes (e.g., `facial attractiveness,` `body shape,` etc.). They repeated this in the summer with the same pictures, and took the same measurements.
They found that in the winter, males tended to rate females as being more attractive than they did the same attributes in the summer. This held true for all attributes except for facial attractiveness, which remained constant between seasons.
The authors, being perception researchers, ascribed a different mechanism to this - They suggest that seasonally, your exposure to body types vary. In the summer, males are exposed to more female bodies than in the winter. Though I'm not sure I agree with their hypothesis, I've an anecdote to illustrate this. I was waiting at ADFG for the winter antlerless permits, like the idiot I was. There were a great number of people in line during that -40 snap we had, and you got to talking to stave off boredom (and to take your mind off the cold we were standing in for hours and hours). I spend quite the while talking to someone named Red (the third Red I've met, not counting people called Kavirliq).
Well, fastforward a bit to when it's only -20°C, and a partner and I were going down a mountain when one of our Snowmachines got stuck. We're trying to get it unstuck, when Red and a few others come down the trail behind us. They graciously help us dig it out of the mess we got stuck on... but I couldn't help but notice that Red wasn't a male, like I'd assumed before. She wasn't wearing all her heavy winter gear, and so you could quite distinctly notice she was a her, albeit a tall "her" with a lower voice, but otherwise unquestionably female. You just couldn't tell before, because all the clothes.
Now this is an extreme example. Most of the time, you interact with people indoors, and they're not wearing carharts, a parka, a face mask, a trapper's hat, musher's mitts and bunnyboots. But humans do tend to wear long sleeves and pants, along with looser fitting garments and bulkier clothes in the winter. This is to contrast with Summer, when it's shorts and T-shirts all around. The authors argue chronic exposure to one setting or the other is what leads to acclimatization, and therefore varying the threshold of `what is attractive.` My own thinking runs more toward seasonal fluctuations of hormone titres, but I've minimal evidence to support this.
Men's attraction to women's bodies changes seasonally.
Pawlowski B, Sorokowski P.