The weather outside is frightful, but your workout will be delightful.

Run in the snow. Don't let cold or snowy trails be a deterrent to running—buy some simple athletic-shoe add-ons that will give your footwear a better grip. Florez likes Yaktrax Pro Traction Cleats for Snow and Ice (from $26 to $32 per pair). These simple rubber devices slip onto your running shoes and provide far greater traction on snow without requiring you to adjust your stride. For greater stability in general, however, Florez recommends running in a slightly more upright position, taking shorter steps, and always scanning the path ahead for icy patches.

Go cross-country. Like snowshoeing, cross-country skiing on flat ground requires little expertise but can demand great effort. In fact, "cross-country skiing is the single most aerobically demanding sport in the world," posits Florez. "It's a total-body exercise that combines both resistance training (pushing your skis through snow) and aerobic exercise (again, pushing your skis through snow)." Rent nonwax cross-country skis at a local sporting goods store, and head out to a park or golf course for an excellent workout that burns calories without requiring skiing expertise.

Play with your kids. Pulling your child around in a sled isn't all that different from pushing him or her in a stroller, points out Florez—it's just tougher, since there's more resistance. But that makes the activity an excellent workout option when your kids are home from school on a snow day and you still want to slip in some exercise. "Likewise, sledding or tubing can work as a workout, as well," he says. "Sure, you're sliding down a hill, but you have to slog back up. Get in 10 or 12 runs, and you'll have put in a light-to-moderate set of hill repeats." Your kids will get some physical activity, too—at least until you carry them home.

See our Winter Survival Guide for more advice on combating winter woes, from soothing a sore throat to serving wintertime soup.