March to April remains dry in central Bhutan but becomes noticeably warmer, though never unbearable, with average highs of around 21 °C and lows hovering around 10. Noted for its wide array of flora, early spring sees the blossoming of magnolias, junipers, gentian and orchids of varied hue. Neither too hot nor wet, many visitors take this time to hike among the many thousands of acres of pristine alpine and sub-tropical broadleaf forests. At almost 1,000 square kilometers, Phrumselengla National Park in the region is known for its many rare and exotic bird species, including the colorful satyr tragopan and beautiful nuthatch. The park's fragile soil has left it almost completely unspoiled by development.
Spring is one of the best seasons to take in and trek the summits of northern Bhutan’s mountains. The average lows are back up to a manageable minus 4 and the highs an acceptable 10 °C.
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. Bhutan’s southern circuit, including the districts of Samtse, Chuka, Dagana, Tsitang, Sarpang, Zhemgang and Pemagatshe form something of an ecological hub and the rich biodiversity make the region an ecological hub, ideal for trekking in tropical forests.