Apple

I had mine (6, maybe the one before - I can’t remember) while camping 2 or 3 years ago in a tent in January. The low one night was around 18°F, and I had the charger on the bottom of the tent, so it was obviously pretty close to the ground. When I woke up, my watch didn’t work. It was showing an error like the battery had died. I left it on the charger at the campsite the rest of the time I was there, in my car the entire ride home (2 hours), and it still never turned on. I went to Apple and bought a new one while that one was being worked on. Apple ultimately said there weren’t any issues - the battery was just dead. 🤷‍♂️

So, mine didn’t fair well.