Botswana lies entirely within the shallow basin formed by the high-lying interior of the southern Africa plateau and is underlain by basement granites, which in turn are covered by the Karroo sedimentary layer within which the Ecca shales are found. These sediments host Botswana’s coal deposits. Diamond-bearing ores are found in volcanic intrusions known as the kimberlite dykes located at Orapa, Letlhakane and Jwaneng. Three-quarters of the land surface is covered by the Kalahari sands. The Okavango Delta, the world’s largest inland delta, is located in the northwest of the country and is characterized by vast areas of open water and wetlands and an abundance of wildlife. North-central parts of the country are dominated by the Makgadikgadi Pans, a large salt pan. Central and West areas of the country are dominated by the Kalahari Desert and grassland and sandy soils; this area is best suited for livestock, as opposed to agriculture. Eastern areas have more fertile soils and grasslands with annual rainfall exceeding 400 millimeters (mm). Overall, the country is arid to semi-arid with highly erratic rainfall. Botswana’s climate is determined by its inland location, astride the subtropical high-pressure belt. During the summer months (November to March) the Inter-Tropical Convergence Zone (ITCZ) brings moisture to the northern areas and becomes progressively drier towards the country’s western areas. The mean annual rainfall ranges from over 650 mm in the northeast to less than 250 mm in the southwest; annual rainfall covers a range from 620 mm in the northern Kasane area to 300 mm in the southwestern Tsabong area. The national average rainfall is 475 mm per year. Most rain occurs in the months from October to April, and falls as localized showers or thunderstorms. Temperatures for the country are generally warm to hot, with mean monthly maximum temperatures ranging from 29.5ºC to 35ºC summer, and 19.8ºC to 28.9ºC in winter. Mean monthly minimum temperatures range from 14.6ºC to 20.8ºC in summer, and 2.9ºC to 11.6ºC in winter.
- Botswana has observed considerable temperature increases and since the 1970s and average temperatures have increased 1.5ºC with central, arid parts of the country’s interior observed to have increased by as much as 2ºC.
- The most noticeable increases in temperature have been observed between November to March.
- Throughout the southern Africa region, including Botswana, an increase in the number of warm days and nights have been observed along with a decrease in the number of cold days and nights.
- Trends in precipitation for Botswana remain highly variable, however an overall reduction in precipitation has been observed for the southern Africa region; characterized by below normal rainfall and more frequent droughts.
- Botswana has observed a reduction in late summer precipitation, primarily from November to March. Changes in the onset, duration, and intensity of rainfall, including increased frequency of dry spells have also been observed.
- This has resulted in an increased frequency of intense rainfall events being experienced, as well as the frequency of more intense and longer lasting droughts. Impacts have been most pronounced in the east and southern areas of the country.