Fur is great but unfortunately in extreme weather conditions, it is not always enough to keep warm and healthy. Make sure that your pet has a dry and wind-free shelter at all times.
When it comes to clothing for winter, coats for dogs are great as long as you take the coat off when temperatures rise and don't leave your dog alone with a coat on - they can get caught in the clothes and injure themselves. Cats usually won't tolerate clothes.
Young pets, senior- and sick pets need to be indoors in cold and wet weather conditions.