in the southwest to 200 metres at the Logone River. The average elevation of this basin is 280 metres. The Diamaré Plain occupies the lower third of the Chad plain and is characterised by a number of isolated inselbergs. The Mandara Mountains at the southwestern border with Nigeria form the highest point, lying between 500 and 1000 metres, with an average of about 900 metres. Mount Tourou is the highest point, at 1,442 metres. These mountains likely arose as a result of the same tectonic activity that gave rise to the Bénoué Depression in the North Province. The area was once volcanically active, as a number of freestanding necks of trachyte and rhyolite of extinct volcanoes attest. The most spectacular of these lie in the valley by the tourist village of Rhumsiki. The part of the range that lies within the Far North is on a middle plateau at about 800–900 metres. Isolated mountains continue into the Diamaré Plain. The mountains' northern extent is hilly, dissected by a number of rivers. Climate The Far North is hot and dry. Beginning at 10° N, the climate is tropical and Sahelian, and rainfall is a relatively small per year, with rains falling a bit more frequently in the Mandara region. South of 10°, the region west of the Mayo Kébi and south to the border with Chad, in the Cameroonian beak. Here, climate is tropical of the Sudan type, with higher rainfalls of per year. Temperatures average , except for the Chad Basin, where they climb to . Actual temperatures of course fluctuate with the seasons, however. At Kousséri, for example, there is an difference between January () and August (). The Far North has two seasons: one dry, and one wet. These are further broken down based on average temperatures, yielding four distinct periods in the Sudan area: dry and relatively cool from November to January as the province experiences a shade of winter from climes further north, dry and hot from January to April, torrentially rainy from April to June, and cool and sporadically wet from June to November. In the Sahel zone, the wet periods are shorter, lasting only five to seven months in the south but shortening toward Lake Chad. Temperatures reach their highest levels from January to May. Beginning at about 11° N, the province only experiences about 25 to 30 rainy days each year. Plant and