upper reaches of the Himalaya, above . Temperate Himalayan wetlands provide important habitat and layover sites for migratory birds. Many mid and low altitude lakes remain poorly studied in terms of their hydrology and biodiversity, like Khecheopalri in the Sikkim Eastern Himalayas. Climate Temperature The physical factors determining the climate in any location in the Himalayas include latitude, altitude, and the relative motion of the Southwest monsoon. From north to south, the mountains cover more than eight degrees of latitude, spanning temperate to subtropical zones. The colder air of Central Asia is prevented from blowing down into South Asia by the physical configuration of the Himalayas. This causes the tropical zone to extend farther north in South Asia than anywhere else in the world. The evidence is unmistakable in the Brahmaputra valley as the warm air from the Bay of Bengal bottlenecks and rushes up past Namcha Barwa, the eastern anchor of the Himalayas, and into southeastern Tibet. Temperatures in the Himalayas cool by 2.0 degrees C (3.6 degrees F) for every increase of altitude. As the physical features of mountains are irregular, with broken jagged contours, there can be wide variations in temperature over short distances. Temperature at a location on a mountain depends on the season of the year, the bearing of the sun with respect to the face on which the location lies, and the mass of the mountain, i.e. the amount of matter in the mountain. As the temperature is directly proportional to received radiation from the sun, the faces that receive more direct sunlight also have a greater heat buildup. In narrow valleys—lying between steep mountain faces—there can be dramatically different weather along their two margins. The side to the north with a mountain above facing south can have an extra month of the growing season. The mass of the mountain also influences the temperature, as it acts as a heat island, in which more heat is absorbed and retained than the surroundings, and therefore influences the heat budget or the amount of heat needed to raise the temperature from the winter minimum winter to the summer maximum. The immense scale of the Himalayas means that many summits can create their own weather, the temperature fluctuating from one summit to another, from one face to another, and all may be quite different from the weather in nearby plateaus or valleys. Precipitation A critical influence on