Book ID 675
McNaughton, Samuel J. A General Tour of the Serengeti National Park, 2000~
Because of the altitude, the temperature is always pleasant.
Daytime high temperatures average a balmy 28o C (81o F), so you can work up a sweat in the sun, and nights are a cool 14o C (57o F), so you sleep under a blanket most nights. Because the humidity is low, seeking shade can rapidly cool off daytime sweat.
But there are strong seasons here. Seasons are not temperature-dependent. Seasons here are rainfall-dependent; a rainy season, and a dry season. The rainy season is normally from November through May, the dry season from June through October. This seasonality is due to the movement of the Intertropical Convergence Zone, a low-pressure system that oscillates over the Equator. When it is directly over the region, rainfall is heavy. However, the strength of seasonality is greatest in the SE, where the Serengeti Plains lie, and least in the NW, where the Isuria Escarpment rises above the plains. There is a rainfall gradient from below 400 mm (16 inches) annually in the SE to above 1100 mm (43") in the NW.
This rainfall gradient is accompanied by a gradient in length of the growing season, around 70 days in the arid SE, while it is near year round in the subhumid NW. Rainstorms are typically due to convective clouds that begin forming in late morning, then condense to a level leading to rain, often resulting in violent downpours in mid-afternoon, then dissipating afterward, leading to sunny evenings.
The map shows isolines of rainfall in centimeters (an inch = roughly two and -Serengeti Rainfall Gradients a half cm) and the annual movements of the migratory herds in relation to the rain gradient. The migrants spend the rainy season, when most young are born, at the lowest end of the gradient. They move toward the west and north between seasons, and spend the peak of the dry season in the far NW, the wettest part of the region.