Bhutan has four seasons, with spring spanning from March to May, summer is between June and August, autumn is from September to November and winter runs from December to February.
The climate in Bhutan is extremely variance. It depends on the altitude. The southern of Bhutan, closer to India is tropical weather which is hot and humid. The northern of Bhutan is cold during winter. The Himalayan mountain peaks are perpetually covered in snow and lower parts are still cool in summer due to the high altitude terrain.
Summer in Bhutan is the monsoon season. The rains are usually heavy, especially in the southern Bhutan. Temperatures can vary between 20 and 30 degree Celsius, cooler in the evenings. It is not good time for trekking but still a good time to visit Haa, Paro, Thimphu, Punakha and surrounding areas of western Bhutan.
Winter in Bhutan can be very cold, particularly in the central of Bhutan. The eastern of Bhutan is warmer than the western of Bhutan. The winters are dry with temperatures may range from 16 degree Celsius in valleys with a clear and deep blue sky. Nights are much colder, sometimes below freezing. Snow is from mid- January to mid-February.
Spring in Bhutan is the season for beautiful flowers and birds. Temperatures will be from 17 to 22 degree Celsius. The temperatures will be 28-30 degree Celsius in the low altitude such as Punakha (1,300m), Wangduephodrang (1,350m).
Temperatures in September will be between 20 and 25 degrees Celsius with some showers, not as heavy as in summer. From the end of September to November temperatures are from 15 to 20 degrees Celsius, nights are very cold. The sky is clear and brisk breeze picking up.
Below is maximum and minimum temperatures in Celsius were recorded from valley floors.