Finally, the lakes froze three or more inches deep. So deep that, with temperatures in the teens or lower, snow did not stick to the surface. It seems magical to me that water I swam and paddled in months ago can serve up a platform for outdoor aerobic exercise in the depths of winter.

I skated as a child, as a mother and, even after my son left home, on the lakes wherever I lived. In New Jersey, we used skate sails, holding them to windward, speeding along the lake surface and peeking through the plastic window of the sail to ensure we didn't collide with our fellow club members. In Minne...