Only two places offer wintertime lodging inside Yellowstone . Mammoth Hot Springs Hotel, on the north end of the park, is the only accommodation accessible by road and has ski and snowshoe trails nearby, while the modern Old Faithful Snow Lodge and Cabins puts you close to the geysers and many miles of ski trails.
Each has a restaurant, lounge, gift shop, and rental of skis and snowshoes. Mammoth has a couple of advantages over Old Faithful: far fewer snowmobiles so it’s much quieter, and road access to the Lamar Valley  where wolves, bison, and elk are major attractions. You might even see a pack of wolves take down an elk.
A wide variety of multi-night Winter Getaway package trips are available out of Mammoth  and Old Faithful , including a “Nordic Heaven” trip ($678 d) that includes two nights’ lodging, snowcoach transportation, breakfasts, plus ski and skate rentals.
In addition, the Yellowstone Association Institute has excellent Lodging and Learning packages throughout the winter, notably a four-night “Winter Wolf Discovery” trip ($1,300 d) that includes lodging at Mammoth Hotel, plus breakfasts and lunches, naturalist-led treks to Lamar Valley, snowshoes, hot tub access, and evening programs.
Get details on various winter lodging, learning, and play options from Xanterra Parks and Resorts (307/344-7311 or 866/439-7375, www.yellowstonenationalparklodges.com ).
The only wintertime camping spot is Mammoth Campground, where temperatures are milder and the snow lighter.
During winter, the most popular—and crowded—times to visit Yellowstone are around Christmas and New Year’s and the Presidents’ Day weekend in February. If you plan to arrive at these times, make lodging reservations six months in advance. The rest of the winter, you should probably reserve at least three months ahead.
Only the Mammoth and Old Faithful visitor centers are open during winter. Free ranger-led activities include evening programs at Mammoth and Old Faithful. Check the winter edition of Yellowstone Today for details, or find it on the web at ww.nps.gov/yell.
Xanterra Parks and Resorts (307/344-7311 or 866/439-7375, www.yellowstonenationalparklodges.com ) offers a variety of guided ski and snowmobile tours and provides wildlife bus or van tours. In addition, the Yellowstone Association Institute (406/848-2400, www.yellowstoneassociation.org ) has outstanding winter classes.
The Mammoth Clinic (307/344-7965) is open daily 8:30 a.m.-5 p.m. June-August, and weekdays—except Wednesdays—in the winter for medical emergencies.
The Yellowstone General Store at Mammoth is open for groceries and supplies year-round, but only meals and gas are available at Old Faithful. Warming huts are at Old Faithful , Madison Junction , Canyon , West Thumb , Fishing Bridge , and Indian Creek (south of Mammoth Hot Springs ). They contain restrooms and snack machines (except Indian Creek and West Thumb), and all are open 24 hours (except for Old Faithful, where other facilities are available). The huts at Madison and Canyon also have snack bars selling hot chili or soup. Park rangers are often at the warming huts during the middle of the day.
Most of Yellowstone’s roads officially close to cars on the Monday after the first Sunday in November and remain shut down all over except for the 56 miles between Mammoth and Cooke City. Roads don’t open for cars again until sometime between mid-May and early June. The roads are groomed for snowmobiles and snowcoaches mid-December-mid-March. The rest of the winter you’ll find only skiers and park personnel on the roads.