Evening frosts are known in summer, and snow or sub-freezing temperatures should be expected in spring and fall. Winter temperatures may drop to less than -40 Farenheit, particularly in higher elevations. Rain or snow storms appear quickly wherever you may be in the Park. Thunder storms rise quickly. If you are on the water or a mountain summit, get off at the first rumble of thunder.
Individual discretion is advised.
Some trails are specifically designated as ski trails. Always ski with extra ski-tips. Winter climbing and hiking gear must include crampons, snowshoes, and on some well-used trails, backcountry skis. Pack a four season tent, insulating pad and winter-rated sleeping bag for winter camping. Whatever the winter activity, dress in layers of wool, polypropylene or synthetic fleece.