Winters in Tibet are cold, but not as much as most people think. The temperatures are quite bearable, especially at lower elevations. Winter starts in November with the drop of temperature below freezing, but days are sunny and dry. It feels warm and pleasant during the day as you get 9 hours of sunshine a day.
The months of December and January are mainly dry with clear skies and warming sunshine. But it can be quite windy and get colder at any time. Although it snows rarely, in the north and western parts of Tibet some roads can be closed due to heavy snow. From February till March Tibet is closed for foreigners. Entry permits aren't usually issued during this period. March is still a cold month, but sunny and dry as well.