With my dog, the colder it gits, the more she needs to run outside.

The stuff we do inside is more just mentally stimulating for the dog. Two things we do are; play go find the toy, and go find somebody. The first one is more like retrieving so just start out easy on the dog so they figure out what you are looking for them to do, and when they do it lavish the praise and or treats on 'em. Tica can find some pretty will hidden stuff now, although it may take 5 min or so of sniffing around vigorously. Do that 3 or 4 times and we are up to 20 min.

With the second, they are learning the names of people in plain view and going over to great them. This one was definitely harder and took more patience to get her to do. But each dog is different; go with your dog's strength and branch out from there. Tug-of-war is another.