The climate of Bolivia is still very briefly known, since only for La Paz and Cochabamba, both cities located on the plateau, there is a sufficient series of meteorological observations. So for most of the Bolivian regions our climate knowledge is based only on data reported by travelers. Following the classification of climates proposed by De Martonne, we can say that there are three main types of climate in Bolivia. The plateau has the kind of climate that De Martonne calls Mexican, hot climate at altitude, with average annual temperatures always below 20 °, with very small annual excursions, with low average extreme temperatures, with frosts and snowfall at more or less great heights, and in which rainfall is noticeable a well-defined dry period. In La Paz, located at 3630 meters above sea level, the average annual temperature is 9 °, 4, the average temperature of the hottest month (November) of 11 °, 5 ° and that of the coldest month (June) of 6 °, 7, with (mean) extremes of 23 °, 5 and −2 °, 9. The amount of rain amounts to 553 mm. annually, and is very unevenly distributed throughout the year: in fact 60% of it falls from December to February; June and July are almost completely free of rain; there are 114 rainy days, about a third of the year. In Cochabamba (2559 meters above sea level), given the much lower height, there is an average annual temperature of 17 °, 6 °, with 6 ° of annual excursion (average temperature of the hottest month, November, 20 °; of the coldest month, June, 14 °). The average extreme temperatures have a greater range than that of La Paz: 30 °, 3 and −20.7. On average, 462 mm fall annually. of rain, of which 85% from November to March. The rainiest month is January, with 107 mm: the driest August, with 4 mm. only. In Sucre (2799 m.) 695 mm were recorded. annual rain, of which 617 from November to April. The rains decrease rapidly, on the plateau, proceeding towards south and west: their distribution during the year, however, is similar to that which occurs in La Paz, Cochabamba and Sucre: thus in Oruro, for example, 70% of the amount falls between April and November. For Bolivia 2012, please check oxfordastronomy.com.
The lowlands of Beni and Mamoré and the eastern side of the Eastern Cordillera up to around the 18th century have, on the whole, that type of climate called by the Guinean equatorial De Martonne. characterized by a very high humidity and strong heat throughout the year, heat made painful for man by the humidity itself. It rains almost every day, in the afternoon; the sky is almost always covered with mist. The rains, very abundant (1500-3000 mm. Per year) have two maximums, which correspond to the two passages of the sun at the zenith. The average annual temperature is about 25-26 ° in the lowlands, about 22 ° on the slopes of the Cordillera around 1000 m. high (region of the yungas). The annual excursions are very small (2-3 °); the hottest month is November, the least hot month is June. The heat, on average, decreases by 1 ° every 400 m. in height. Proceeding from the west towards the upper Guaporé, we begin to notice not only a decrease in the quantity of rains, but also the advent of a dry season, which is also the hottest, and an increase in the annual excursion. Here we have a Sudanese sub-equatorial climate zone, an area that extends southwards, including most of the Bolivian Chaco. On the Chiquitos plateau the average annual temperature is 25-26 °, and the rainfall varies between 1000 and 1500 mm. annually and fall mainly from November to April (70-80% of the quantity); proceeding southwards the trend of temperatures becomes more and more irregular, the rains decrease and the dry season is accentuated. The Bolivian Chaco receives nowhere more than 1000 mm. of rain (2/3 of which from November to April), indeed in the southernmost part, which passes to the dry northern region of Argentina, considerably less. The average annual temperature is 24-25 °, with an excursion of 8-9 ° between the hottest and coldest months. The average of extreme temperatures exceeds 40 ° on one side.