Most of the country falls into a plateau region, which gives Zambia a moderate, pleasant climate, despite the fact that it is within tropical latitudes. The valley of the Zambezi River is a low-lying area, which runs the length of the western and southern borders with a hotter and more humid climate. In the river valleys of the Zambezi and Luangwa, it can become very hot in the month of October. The extreme northern areas have a more usual tropical climate as they reach the shores of Lake Tanganyika. Despite the tropical location, the altitude of the Zambian plateau ensures a comfortable climate throughout the year except in the river valleys where it is markedly hotter. There are three main seasons: April to August is cool and dry; September to October is hot and dry; and November to March is warm and wet. Only during the wet season is there noticeable humidity.