It's a virus not a bacteria so the proteins don't disintegrate. The probability of transmission outside is small as sensibly people limit the time outside, but the flipside is they stay indoors, in confined spaces together, which is perfect breeding ground for the virus.

Cold acts as a preservative for viruses. In labs which do experiments with viruses, they keep viruses in freezers for a looong time.

Last I heard the coronavirus survives a lot longer in freezing conditions than at room temperature.

Coronaviruses cause the common cold, which is more common when it's cold.