 The thermal equator, which matches the hottest spots year-round on the planet based on the mean daily annual temperature, crosses the country Most of Mali receives negligible rainfall and droughts are very frequent Late April to early October is the rainy season in the southernmost area.During this time, flooding of the Niger River is common, creating the Inner Niger Delta.The vast northern desert part of Mali has a hot desert climate (Köppen climate classification "BWh") with long, extremely hot summers and scarce rainfall which decreases northwards.