There is no single “best” exercise for fall, or any other time of year for that matter. As long as you are active is the key. Find an exercise you enjoy and take it outdoors to mix things up. Besides the typical jogging, walking and cycling try weight training outside. The cooler temperatures and fresh air will add new vitality to your workouts.
Take your workout to the park – jog or bike there, perform chin ups on the monkey bars, push ups, body weight squats, etc then jog or bike home. It’s a great way to work out and even take a friend or the kids along!