Bhutan's climate ranges from tropical in the south, to temperate in the center of the country, to cold in the north...and like much of your adventure in the Himalayas it will be quite unpredictable. In the Thimphu and Paro valleys, the winter daytime temperature averages 60 degrees Fahrenheit during clear winter days but drops well below freezing during the night. Mid December to early January can be a beautifully clear and dry time in Western Bhutan. Late December through mid February is the period of heaviest snow fall in the higher elevations.