A central east-west mountain range dominates the geography of the island of New Guinea, over in total length. The western section is around long and across. The province contains the highest mountains between the Himalayas and the Andes, rising up to high, and ensuring a steady supply of rain from the tropical atmosphere. The tree line is around elevation and the tallest peaks contain permanent equatorial glaciers, increasingly melting due to a changing climate. Various other smaller mountain ranges occur both north and west of the central ranges. Except in high elevations, most areas possess a hot, humid climate throughout the year, with some seasonal variation associated with the northeast monsoon season.