Claim this achievement if you reach a hash using cross-country skis. Using cars, snowmobiles, dogsleds, etc, to go part of the distance is not allowed (this includes being pulled by such a vehicle). To avoid damaging your skis, you may take them off and carry them over roads and through urban areas. However, at least half the distance must be traversed on skis - you can't just carry them around and call it a Ski Geohash!
Rollerskis are acceptable, as are waterskis (but you must not be pulled by any vehicle). Duct taping two-by-fours to your feet might also work. Downhill skis can be used, but you may not use a ski lift to get to the top.
Bonus points if you achieve a Ski Geohash in the summer.