The weather in Tibet is most temperate from May to November, though the rains of July and August make some roads impassable. Average daily temperatures in Tibet range from the high 50s to the low 70s. Nighttime temperatures are often 20 or even 30 degrees lower, so even in August the weather in Tibet necessitates a light coat at night. From December to March, temperatures rarely make it above 50 degrees and the wind chill can make it feel much colder. Snow is inevitable at high elevations in the winter, but towns in the valleys like Lhasa and Shigatse usually have mild winters, not white ones. Temperatures while trekking in the mountains tend to be more extreme than in the towns.