October to December, it suddenly becomes dry again and starts to cool. Although average highs are still a balmy 18 °C during the season, by late November it falls close to zero at night. However, the warm dry days make it a fine time to visit and the many ancient trees across the nation's national parks start to take on spectacular color. The seasonal dry weather sees the start of the vibrant Tshechu festivals, celebrating the 10th day of an autumn month in the lunar calendar (the date varies in the western calendar). Masked dances take place in different districts on different days. The Tshechu are dances based on morality tales of ancient Bhutanese saints. The social gatherings take place over several days and are a way for scattered villages to bond, and a delight for intrepid travelers.
The autumn months are the best time to visit northern Bhutan. The rain stops and skies turn clear and blue, providing spectacular views of Bhutan's unspoiled mountains. With the clearing of the monsoon mud, trekking seasons starts, and some of the most isolated hiking routes on the planet become open, including the Snowman Trek, one of the most challenging in the world. There are less locals and tourists in these northern regions than, say, Tibet or Nepal, and the isolation here is such that one can trek for days without encountering so much as a village.
The climate in southern Bhutan is hot and humid ranging from 15 to 35 degree Celsius throughout the year. Virtually any time of the years is good to visit.