Weather in Bolivia varies with altitude rather than season.
The country sees two seasons, winter or dry season which runs between May and August and summer or rainy season which takes place November through March.
Springtime (September-November) is considered the best time to visit the country with sunny days and clear skies, still not too cold in the salt flats and the desert.
Summer or wet season (November-March) brings heat, humidity and mosquitoes, especially in the Amazon where roads can be impassable. However, rain is less frequent in the Altiplano and everything looks lush and greener.