Spring (mid February- March – April), Autumn (September – October) and early Winter (November) are the best time to visit Bhutan. Northern Bhutan lies close to the Himalayan mountains and this makes it much colder than the rest of the country. The region receives snowfall during winter. Southern Bhutan with its tropical climate is the warmest. During the monsoon season (June to August) there is heavy rainfall and humidity. The endangered Black-Necked Cranes migrate to Phobjika Valley from Tibet during late October. October to mid-February is the ideal time for bird-watching tours.