I wish people would stop doing that. I live 'way out in the country and there are still enough people around here with "outdoor" cats that I rarely see any ground-nesting birds. Cats are extremely destructive on wildlife. When entire classes of birds are wiped out by cats just for the fun of it, our ecology suffers.Always let my cats out come rain or shine, there pretty good at coping with the weather.
They seem to have an innate ability to find somewhere to snuggle up in.