The climate of India is mainly tropical because it lies between the Tropic of Cancer and the Equator. India hosts six major climatic subtypes, ranging from arid deserts in the west, alpine tundra, and glaciers in the north, and humid tropical regions supporting rain forests in the southwest and the island territories. The country's meteorological department follows the international standard of four seasons with some local adjustments: winter (December to February), summer (March to May), monsoon or rainy season (June to September), and a post-monsoon period (October and November).