The best time to visit Mao is October through April, when the monsoon has finished and the skies are generally clear. The elevation keeps temperatures moderate year-round: summers are pleasantly cool (rarely above 25°C), and winters can be chilly, with temperatures dropping to around 5°C at night in January and February. Frost is not uncommon on the higher ridges.
The monsoon (June–September) brings heavy rain and can make the roads unpredictable. Landslides occasionally close National Highway 2 for days at a time during particularly heavy rainfall. If you are travelling through in the wet season, build flexibility into your itinerary.