Bhutan- Climate and season is certainly a consideration when planning your trip to Bhutan. The ideal time for trekking, tours and for travelling throughout the country is Autumn, from late September to late November, when skies are generally clear and the high mountain peaks rise to a vivid blue sky.
Spring, from March to May, is recognized as the second best time to visit Bhutan for touring and trekking. Though there are more clouds and rain than in the autumn, the magnificent rhododendrons, magnolias and other wildflowers are in bloom and birdlife is abundant. You can get occasional glimpses of the high peaks, but these are not the dramatic unobstructed views possible in autumn. Spring is also the time of the magnificent Paro tsechu.
Summer, from June to August, is the monsoon season. Monsoon is very heavy, rain falls is 500mm in Thimphu and surrounding sites. Thus, it is not considered as the good time to travel to Bhutan.
The winter is a good time for touring in western Bhutan, bird-watching in the south’s subtropical jungles, and whitewater rafting. The days are usually sunny, cool and pleasant, but it’s quite cold once the sun sets and you will need to pack warm clothing.