We have always wanted to visit Yellowstone in winter, but since that is also school season it is tough to do. Snowmobiling in the winter is more adventurous than driving the roads in the other seasons, but your definitely need the right equipment and clothing! If you have your own snowmobiles and gear, you can apply for a private non-guided permit to ride your snowmobile through the park for up to 3 days.
The permit applications are open September 1-30, and they are available at recreation.gov. Just follow the link and type 'yellowstone snowmobiles' in the search bar. Costs are $6 to apply and $40 per day for each day of your stay. If you go, drop us a note to tell us about it!