When it’s cold outside, it’s harder for your kids to get the exercise they need. They’re probably not spending as much time in the back yard and may no longer be walking home from school. Sometimes recess is even cancelled. Now is the time to look for recreational activities indoors.
Swimming. One of my kids’ favorite winter activities is swimming. There’s probably an indoor pool somewhere near your community and they’re a lot less crowded than they were during the summer months. Swimming is a total body workout and playing in the water will wear kids out quickly.
Roller skating may have fizzled in popularity since the 70s, but there are still roller rinks around and kids still love them. Rent skates and blades or bring your own. Some rinks even allow scooters on the floor. Your kid will learn balance and get a good workout. Most roller rinks have discount days. Look online for the best deal day for you.
Climbing. There are a lot of indor rock climbing places and kids are naturals at this sport. (Aren't you always telling them to stop climbing on things?) They have a great upper body strength to weight ratio. Some places even have special wall areas just for kids. Besides traditional rock climbing venues, you can often find indoor rock walls in gyms and large sporting goods stores.
Sports. There are plenty of sports you can sign up for that take place indoors. Basketball, volleyball, gymnastics and martial arts to name a few.
All of these things will cost some money, but there are plenty of free ways for your kids to get exercise when it's too cold to go outside. See this post for some ideas.