When is the best time to trek in Bhutan?

The best times to trek in Bhutan are March to May and September to middle November, in another word, the best seasons to trek in Bhutan are spring and autumn. Although the temperature drops to around -10 degrees Centigrade at night, the daytime is very warm. All trekking activities take place during daytime, when the temperature is around 20 degrees Centigrade.