Tibet during Chinese New Year

In Lunar New Year the temparature in Lhasa and most Tibetan regions would be 15 degree centigrade in the day time, 0°C at night. In the Everest Base Camp, the temparature will drop to -10°C at night and 0°C in the day time. I think it's bearable...no problem..
It's the least crowded in Tibet in Feb. cause Chinese people stay at home celebrating luna new year with their family.

Good time to go.

I have spent about a month in Central Tibet (Lhasa-Everest-Nepal border area) for 6 of the past 8 years. During Chinese New Year there are very few tourists in Lhasa. Though the temperatures in Tibet are cold in winter, most places where travelers go are warmer than you might think.

I highly recommend going to Tibet during the low season. Read the following article for reasons why:
Low Season: The time to go to Tibet

I agree with the above comments. The winter, including the week of Chinese New Year celebrations, is a pretty good time to be in Tibet. There will be very few other tourists (and very few Chinese tourists), which is good.

Many of the smaller Chinese run stores/restaurants will be closed for the first week or two of the new year, as the Chinese workers head back to "mainland" China to celebrate with their families. That does make cities like Lhasa look more desolate, but it also makes it, in certain respects, more bearable.

Contrary to other Chinese tourist spots, Tibet are not really popular for Chinese tourists during Spring Festival (3 Feb 2010 this year) or even during the National Day Golden Week (1 Oct every year).

So you won't see a big crowd.