Oh...I'm so sorry. I'm praying that he's returned or that he will return. I feel your pain and loss.
He probably ran away to a home where he could go inside.
I don't think so. Labrador retrievers have thick coats designed to protect them from the cold and wet. When I'm bundled up and shivering on a windy, icy day, Charlie is invigorated. He enjoys being outside.