Bolivia - Climate
Although Bolivia lies entirely in the tropics, extreme differences in altitude and rainfall give it a great variety in climate. The mean annual temperature of La Paz, at 3,697 m (12,130 ft), is about 8° C (46° F ); that of Trinidad, in the eastern lowlands, is 26° C (79° F ). In the western highlands, cold winds blow all year round; at night the temperature often drops below freezing, but the sun is intense and the air brilliant during the day. The rainy season lasts from December to February, but during most of the year the high Altiplano plateau is parched and inhospitable. Around Lake Titicaca, rainfall is adequate, but there is less than 13 cm (5 in) a year in the extreme southwest. The fertile valleys in the Cordillera Oriental have a warmer, semiarid Mediterranean climate.
The Yungas and Valles have a semitropical, moist climate that gradually becomes hotter as one descends from the eastern slopes of the Andes to the tropical eastern lowlands. Rainfall is heavy in the northeast, and floods are common in March and April. The lowland plain becomes drier to the south, until it reaches drought conditions near the Argentine border.