The Republic of South Africa extends from 22°S to 35°S at Cape Agulhas, the most southerly point of the African continent. Much of the interior consists of extensive high plains, known in South Africa as 'veld', with an altitude between 900 m/3,000 ft and 1,800 m/6,000 ft. The interior is divided from the narrow coastal plain by a steep escarpment (The Great Escarpment) forming lofty mountains in the east and south. The eastern shores of southern Africa are warmed by the Agulhas current, which flows southwards from tropical latitudes; while the western shores are cooled by the Benguela current, flowing northwards from the cold southern ocean surrounding Antarctica. These influences of relief and ocean currents produce a distinctive pattern of climatic regions which cut across the political boundaries separating the Republic from its neighbours.
Both the southerly latitude and the altitude of the interior regions produce a temperate climate such that only the low-lying districts in the northeast, along the border with Zimbabwe and Mozambique, have a climate that is tropical. The southern part of South Africa is sufficiently far south to be influenced in winter by weather disturbances associated with the belt of westerly winds in the southern ocean. For this reason a small portion of the southwestern Cape Province, below the Great Escarpment, has a Mediterranean type of climate with mild, changeable winters, during which most of the annual rainfall occurs, and a warm to hot, sunny summer. Eastwards of Cape Town this merges into a region where some rain occurs in all months but where temperature conditions are similar. In the coastlands of KwaZulu-Natal and the lowlands below the Great Escarpment up to the border with Mozambique, the climate becomes almost tropical; winters are warmer and summer is the wetter season, although rain falls throughout the year. This coast is exposed both to warm water offshore and the southeast trade winds for most of the year.
By contrast the west coast northwards from about 32°S is a desert region with a remarkably small annual temperature range. This is because the cold Benguela current chills the air and produces atmospheric conditions unfavourable to rainfall; fog and low cloud are frequent along this coast.
In the interior of South Africa there is a broad contrast between east and west. Total rainfall is greatest in the east and gradually decreases westwards so that much of western Gauteng Province and the Western, Eastern, and Northern Cape Provinces are semi-desert with a low and unreliable rainfall. The wettest regions are the eastern parts of Gauteng and the Free State, where both altitude and exposure to the moist air coming off the Indian Ocean produce the heaviest and most reliable rainfall. Over the whole of this interior region rainfall comes mainly in the summer season, much of it in thundery downpours. Because of the altitude and the 'continental' influence there is a large daily and seasonal range of temperature so that frost is a frequent occurrence in winter and snow is by no means unknown above 1,500 m/5,000 ft. Winters are predominantly dry and sunny and summers warm to hot.
The greater part of South Africa has a very sunny climate with much fine, settled weather. The southern coastal regions have their most disturbed and changeable weather in winter and the eastern coastlands and the interior their most disturbed and rainy weather in summer. In few parts of South Africa are the weather and climate unhealthy or likely to cause great discomfort or stress. Daily sunshine hours are high over most of the country, averaging eight to ten hours a day around the year. The cloudiest regions are the western and eastern coasts, particularly in the summer months.
The Eastern Interior or High Veld
Including (with towns and cities in parentheses) the greater part of Gauteng (Pretoria, Johannesburg) and the Free State (Bloemfontein).
Most of this area is above 1,200 m/4,000 ft. This is the most developed part of South Africa. As the tables for Pretoria, Johannesburg and Bloemfontein show, the winters are dry and mild but with frequent cold nights. Summers are warm with more frequent rain, but temperatures are rarely excessively high. The low humidity and large number of sunshine hours make for a pleasant and healthy climate for most of the year.
The Western Interior
Including much of the interior Cape Provinces and the western fringe of Gauteng.
The chief feature of this large region is its low rainfall; much of it is semi-desert or even desert. Apart from the low rainfall the general features of weather and climate are similar to those of the eastern interior. The tables for Francistown in northeastern Botswana and Windhoek in the higher districts of Namibia are representative of much of the region.
The Namib or Coastal Desert
Including the coast of Western Cape Province above 32°S.
Weather and climate in this desert, which continues north along the entire coast of neighbouring Namibia, are unusual and quite distinctive. The region receives very little rain and is a complete desert, but temperatures are kept low most of the time by the cold Benguela current. On a few days each month, particularly in winter, midday temperatures rise quite high when the berg wind blows from the interior. This is a föhn-type wind bringing very dry air, which is heated as it descends to the coast. Apart from the rare shower of rain and the frequent coastal fog, the berg is almost the only weather feature of this arid region (see the table for Walvis Bay in Namibia).
Southwest Cape Province
Including the coastal lowlands and southern slopes of the mountains around Cape Town.
The coastal lowlands and southern slopes of the mountains around Cape Town have mild and generally wet winters with much changeable weather and dry, settled summers similar to the climate of much of the Mediterranean or California. Summers are not completely dry and occasional rainstorms occur. The table for Cape Town is representative of this region, but inland some sheltered areas are warmer and drier. This was the area first settled by Europeans in the 17th century; French Huguenot settlers introduced the grape vine, which grows well in this climate.
The Eastern Cape
Including the lowlands and hilly region below the Great Escarpment in Eastern Cape Province.
The weather and climate of this region are intermediate between those of the southwestern Cape and the eastern coastlands regions. The main difference is that rainfall is well distributed around the year and disturbed weather can occur in both winter and summer (see the table for Port Elizabeth).
The Eastern Coastlands and Low Veld
Including coastal and inland KwaZulu-Natal.
This is the part of southern Africa where the climate comes nearest to being tropical. The summers are warm and humid on the coast, particularly towards the north in Zululand, where conditions are similar to those found in southern Mozambique (see the table for Maputo). Summer is the wettest season but some rain falls in all months. The table for Durban is representative of the coastal lowlands. The heat and humidity are here moderated by daily sea breezes but conditions are often sultry in summer. Winters are mild to warm. Inland, and at medium altitudes below the Great Escarpment, temperatures are lower, particularly in winter, but rainfall is greater (see the table for Mbabane in Swaziland).
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