I think everyone needs to take their environment into account and be flexible with exercise
Personally I find the winter most challenging for my Beasties. Bitter cold and RAzz needs to be carried pretty soon, but my BRT';s think it's nirvana. But all have to have paws checked, ice balls removed etc after a good romp in the snow; even if that romp is in our backyard!
Swimming in indoor pools we do, about once or twice a week. It is approx a 3 for 1 exercise. That being 10 minutes of swimming roughly equal to 30 minutes of walking.
Playing inside the house, tricks and training also counts. Some can do modified agility exercises in the house.
Stair climbing is good for both you and your dog
Many ways to get exercise in the bad and cold days of winter