does cold weather kill viruses?

yes. sort of.

first, viruses tend to react badly to water. when you hear about water-borne viruses, they tend to either come from a host like a mosquito (who like standing water) or they end up embedded in a medium like animal feces. viruses are just protein - they will dissolve in running water. you should still use soap, as the ph reaction helps increase the efficacy, but water alone will kill the bulk of it.

second, while viruses may freeze in cold weather, the thaw process kills the bulk of them. and, this is where some shift in mindset is necessary.

anything that kills a virus will kill a percentage of the amount of it. so, if you wash your hands in lukewarm water, you'll kill most of it, but you'd have to do it for a really long time to kill all of it. and, if you increase the temperature, you'll kill more of it. and, if you add soap you'll kill even more of it. but, even washing your hands vigorously with soap in hot water for a long time is still probably only going to get 95% of the shit off of them - because your hands are filthy, no matter how hard you try.

you hear about viruses being thawed out in the ice, but it's the epsilon that's left. like washing your hands, the freeze-thaw process will only kill about 95% of the virus, leaving that little bit for scientists to go looking for.

so, is cold weather effective at killing viruses? yes - if cold means below freezing, and you're talking about surface contact or airborne particles. obviously, that doesn't hold once you get inside. but, the effectiveness of freezing weather is basic chemistry. and, don't listen to the people suggesting otherwise.