Botswana's Climate

General Facts

Botswana lies between latitude 18°S and 27°S and longitudes 20°E and 29°E with area 582,000 square kilometers. It is a land-locked country about 675 km inland form the Indian ocean and 1025 km form the Atlantic. It has an average elevation of 1000 m but lower than that of the plateaus of Zambia to the North, Zimbabwe in northwest, South Africa in the southeast, and South Namibia to the west. Highest hill being the Kanye Hill at 1491 m with no barriers of the low of mountain. Botswana enjoys a warm and dry tropical climate with semi-ari lands.

Rainfall

Mean annual rainfall varies from maximum of 650 mm in Kasane to a minimum of less than 250 mm is the Kgalagadi (Tsabong).

Rainfall Seasons

i    Dry Season: May to August.

ii   Pre-rainy Season: September to October.

iii  Rainy Season: Novermber to March.

iv  Post-rainy season is April.

In all seasons, two high pressure systems in the Atlantic and one over the Indean ocean cause subsidence over Botswana and Southern Africa resulting in an arid to semi-arid climate.


Mean, Maximum & Minimum Annual Rainfall - selected Stations
Station Period Mean (mm)  Max (mm)  Min (mm)
Gaborone 1922-86 531.1 925.3 243.2
Francistown 1921-85 462.5 897.9 114.4
Kanye 1925-85 516.6 970.6 104.7
Kasane 1922-85 676.9 1405.6 298.7
Molepolole 1924-85 495.1 914.0 100.2
Maun 1922-85 463.4 1183.9 193.0
Lobatse 1921-85 555.7 1070.4 262.1
Shakawe 1945-85 531.1 1091.4 221.8
Mochudi 1925-85 490.9 888.8 72.9
Ghanzi 1922-85 432.1 698.2 122.2
Mahalapye 1912-85 464.9 891.3 143.9
Tshane 1958-85 347.5 756.7 145.2
Serowe 1921-85 455.5 978.7 194.5
Tsabong 1939-85 290.4 706.0 134.0


Drought

Botswana suffers drought in some years with one of the worst drought in the year 1981-1987.

Temperature

Since Botswana has a large desert area known as Kgalagadi, the diurnal (daily) variation of temperature is large with hot day temperature and cooler nights.

Highest Maximum & Lowest Minimum Temperatures - selected Stations
Station Highest Max. Lowest Min.
Gaborone 43.9 °C -6.5 °C
Mahalapye 40.6 °C -6.0 °C
Francistown 41.1 °C -6.5 °C
Maun 41.7 °C -5.8 °C
Shakawe 39.6 °C -6.1 °C
Ghanzi 42.2 °C -8.5 °C
Tshane 41.0 °C -8.0 °C
Tsabong 42.6 °C -15.0 °C


The hottest months are December and January; the coldest months are June and July.

Relative Humidity

Relative Humidity is maximum in the early morning with about 70% and minimum in the afternoon with 30-40%.

Thundershowers

On the average there were 75 thunderstorm days a year in Gaborone with a higher frequency from October to January and decreased from February to April.

Strong WInds

At the old Gaborone Airport, a ground squall with maximum wind of 70 knots (130 km/p.h.) occured at 17:10 local time on 28 December 1980. At Sir Seretse Khama Airport, a gust speed over 80 knots (148 km/p.h.) was recorded on 26 Dec. 1985.

Winds and Pressure

In Botswana surface wind are predominently easterly to north easterly except in the south west of the country, in Tshane and Tsabong where northerly winds are dominant Calm conditions are also observed in a large number of occations. Forenoon pressure is higher than afternoon pressure at all stations.

Sunshine Hours

Mean annual sunshine hour varies from 8.2 to 9.7 hours/day or 75 to 81% at all stations which means each station receives a large amount of sunshine per day.
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