Winter Weather & Outdoor Dogs
While I agree that the ideal situation for dogs and cats during the winter is a nice, warm bed in the house, please keep in mind that drastic changes in temperature can sometimes do more harm than good. If you bring an outdoor pet indoors, keep it inside for longer than overnight. They get used to the indoor temp, and putting them back out first thing in the morning (the coldest part of the day) is subjecting them to a super drastic change in temperature. It's not healthy for them. They do acclimate to the cold (or heat), and drastic changes complicate things for them.
The best options for outdoor animals is warm bedding, lots of water, a barrier from the cold, and providing extra feed during the winter months. Assuming, of course, that remaining indoors is not an option.