Weather in Sikkim
Sikkim has one city tracked on Mausam Online: Gangtok. Live weather, hourly forecasts and air-quality data are available on its page.
Climate & seasons
Sikkim rises from warm river valleys in the south to the snows of Kangchenjunga on its border with Nepal. Gangtok and the middle hills have mild summers and cool winters, and the monsoon is long and heavy: most of the year's rain falls from May to September, heaviest in June and July, and landslides often close roads. The high north is cold and snowbound for much of the winter.
When to visit Sikkim
The clearest weather comes after the monsoon, from October to December, when mountain views are at their best; spring, from March to May, is also popular, with rhododendrons in flower on the higher slopes.
Air quality in Sikkim
Gangtok's page, linked above, tracks PM2.5 and PM10. Sikkim follows the broader South Asian pattern — cleaner air in the monsoon, more pollution in winter.