Undoubtedly, Tibet is one of the harshest places for human existence. It is cool in summer, but excruciatingly cold in winter. In Lhasa, the relatively humane city in Tibet, although the temperature may exceed 29 degrees C (84 degrees F) in summer, it can also plummet to minus 16 degrees C (3 degrees F) in winter! Solar radiation is extremely strong in Tibet. The sunlight in Lhasa is so intense that the city is called Sunlight City. The thin Tibetan air can neither radiate nor absorb heat, resulting in temperature extremes during both day and night. However it is not impossible to visit the holy snow land. The period from April to October is the best time to visit Tibet, avoiding the coldest months from December to February.