The vast majority of Yosemite visitors go to the park in spring, summer, and fall. That means that the winter season is left to the rest of us, and we get to see the park at its most peaceful and serene. Be sure to carry chains, or check with us in advance to rent/reserve some.
All the main roads are kept well plowed into the Park, except for Tioga Pass Road from Crane Flat to Lee Vining and the Glacier Point Road past Badger Ski Area. Both are closed in the winter.