Some people tolerate cold better than heat. I tolerate heat much better than cold. Body composition and body size play a role. So do heat acclimation and general fitness. I know it’s possible just to wear more clothing in the winter, but you still have to breathe in the cold air. And I don’t like having to wear all those layers in the winter. It’s tricky with layers for winter runs. Sometimes my head and hands get cold and I need a beanie and gloves. Or I only need them for the first half of a run, but then I have to carry them. (My feet never get cold on winter runs, even though I don’t wear socks with my running shoes.)
On the bike, I have a lot of issues with cold hands and toes in the winter. Chemical warmers don’t help that much. Bar Mitts and neoprene covers on the brake levers help a little, but not after an hour or so, on the coldest days. (I’ll probably do more indoor bike workouts this winter, except on moderate days.)
The main issue I have with summer is the greater risk of sunburn (longer days, sun overhead) so I try not to do as many midday workouts now.
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