You can visit Bhutan any time of the year. Because of its elevation, Bhutan is never very hot. July and August are low season because of the rain, but it is also warmest. November to February can be chilly, but they are also very dry.
Bhutan’s climate ranges from tropical temperatures in the south and centre of the country, to cold in the north and like much of your adventure in the Himalayas it will be quite unpredictable from day to day or within the same day. 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 in West Bhutan. Late December through mid February is the period of heaviest snow fall in the higher elevations.
The fluctuations are not quite so great during the summer and daytime temperature often rises to the mid-eighties. Punakha and central valley’s are lower than their Western neighbors and tend to always be a few degrees warmer. The higher peaks will be snow-covered all year. The higher passes, particularly Thrumshing La, between Bumthang and Mongar, can be treacherous during winter as snow falls frequently and ices up the road. Light snow will often dust Thimphu and Paro in winter, occasionally there will be heavy snowstorms despite their location in the Central Himalayas.
The summer monsoon from the Bay of Bengal affects Bhutan from late May to late September. Views over the Himalayas from the higher passes are usually obscured from June to August. There are notable advantages to visiting Bhutan during the wet season including the spectacular rhododendron blossom from March through May and the deep green valleys. Many species of wild orchids are in full bloom during late summer season (August).
The spring season in Bhutan can only be compared to an artist’s palette, truly a spectacular time. The autumn season, late September through November, is usually very mild and clear. The sky is usually at its clearest, displaying magnificent views of the Himalayan range. The spring and fall seasons are traditionally the most popular times to visit the Kingdom.
River rafting can be done March-May and October-December.
Monthly Averages (Paro)