The Maldives has a tropical-monsoon climate, which is affected by the large landmass of South Asia to the north. The presence of this landmass causes differential heating of land and water. These factors set off a rush of moisture-rich air from the Indian Ocean over South Asia, resulting in the southwest monsoon. Two seasons dominate Maldives' weather: the dry season associated with the winter northeastern monsoon and the rainy season which brings strong winds and storms. The shift from the moist southwest monsoon to the dry northeast monsoon occurs during April and May. During this period, the northeast winds contribute to the formation of the northeast monsoon, which reaches Maldives in the beginning of June and lasts until the end of August. However, the weather patterns of Maldives do not always conform to the monsoon patterns of South Asia. The annual rainfall averages 254 centimetres (100 in) in the north and 381 centimetres (150 in) in the south.