Most visitors to Yellowstone go in the summer, which is why the winter is the best time to go. The geothermal geysers and springs, steam vents and mudpots are still hissing and burbling. Tour the park in a Park Service bus on tractor treads or drive a rented snowmobile to lunch. The frozen beauty of the land dotted with snow-dusted bison and punctuated at night by the cry of gray wolves make winter the favorite season for park employees. That’s the only endorsement you should need.