Niger, one of the hottest countries in the world, has three basic climatic zones: the Saharan desert in the north, the Sahel to the south of the desert, and the Sudan in the southwest corner. The intense heat of the Saharan zone often causes the scant rainfall to evaporate before it hits the ground; at Bilma, in the east, annual rainfall is only 2 cm (0.79 in). On the average, rainfall in the Aïr Massif is limited to a maximum of 25 cm (10 in) annually, and most of it comes during a single two-month period. At Agadez, in the northern Sahel, annual rainfall averages 16.5 cm (6.5 in), but yearly totals often vary greatly. In the south, rainfall is higher. It averages 56 cm (22 in) at Niamey, in the southern Sahel, and 87 cm (34 in) at Gaya, in the Sudanese zone. The rainy season is from May through October, with most rain in July and August. At Niamey, the average maximum daily temperature fluctuates from 31° C (88° F ) in August to 41° C (106° F ) in April. Nights are cool (below 20° C /68° F ) from November to February.