Skiing was a winter activity.
In 2024, Christopher Brynner went skiing on Mount Cook in New Zealand. Two guests at a party he held later that year told him they had had to cancel a skiing trip to the Alps, due to political trouble in Europe. (DS9: "Past Tense, Part I")
In 2364, Wesley Crusher and eleven other students were given skiing lessons by a ski instructor in a holodeck simulation of the Denubian Alps. In their time spent in the holodeck, the field trip was exposed to the Quazulu VIII virus. (TNG: "Angel One")
In 2373, Chakotay and several crew members on the USS Voyager went skiing on a holographic recreation of the Ktarian glaciers to relax after their encounter with the macroviruses. Kathryn Janeway, despite a love of skiing, declined an invitation to this, as she felt she'd had enough of a workout recently in fighting the macroviruses. (VOY: "Macrocosm")