Hit the Pool
So you're not a triathlete or competitive swimmer. No worries. You can still head to your town's indoor pool and get a great workout in.
Swimming is considered a super cross-training workout for runners. Really, though, swimming laps at the pool is good for anybody who wants to boost their winter fitness.
Quick tip: Your technique means a lot when you're swimming. Get a swim lesson from a coach before regularly doing laps. Otherwise, your flawed form could force you to fight yourself in the pool.
Create Your Own Race
If the outdoors isn't going to happen due to cold weather, go inside and get creative.
Some health clubs, like the Carondelet Park Rec Complex in St. Louis, Missouri have indoor triathlon events in the wintertime. In Carondelet's case, it's a 500-yard swim in the pool, followed by a 9-mile bike ride on the exercise bike and a 5K on the treadmill. (http://www.active.com/triathlon/st-louis-mo/carondelet-park-rec-complex-indoor-triathlon-2011) It's not quite the same as an outdoor triathlon in the summer, but it can be a fun way to fill up your winter months and give you a time goal to shoot for.
Even if your health club doesn't do something like this, you can set one up yourself, and train for it like you would an outdoor race.Search for a cycling event