Between the escarpment and the coast lie the Great Karroo and the zone of fold mountains to the south, the south-eastern area to the south-east and the low country in the north-east about the Limpopo river and to the west of the Lebombo range. For descriptions of the geological formation of the country see the articles on CAPE COLONY, NATAL and ORANGE FREE STATE.
Owing to its situation in the southern hemisphere, its elevation and its comparatively narrow shape, South Africa is cooler than most places in the northern hemisphere, which are the same dis tance from the equator. The mean annual temperature is remark ably uniform everywhere, because the country, to a large ex tent, increases in altitude as it decreases in latitude. At the meteorological station at Cape Agulhas, 5o ft. above sea-level, and situated 50' S., the mean annual temperature is ; at Johannesburg, 5,750 ft. and 26° if S., it is 6o.6. The highest mean annual temperature is recorded at Komatipoort, 46c) ft. above the sea, and situated on the borders between the Trans vaal and Portuguese East Africa : the lowest is for a sta tion on Table Mountain (Cape Town), 2,496 ft. The area with a mean annual temperature of 71° is confined to a coastal strip of northern Natal and Zululand, and to the low veld of the northern and eastern Transvaal. Ocean currents affect the tem perature of the coastal districts. Along the west coast flows the cold Benguela current, and Port Nolloth, 29° 16' S., has a mean annual temperature of 57.5°. The effect of the warm Mozambique current along the east coast is to be seen in the mean annual temperature of 70.8° for Durban, 29° 57' S.
Mean temperatures, however, are liable to mask important differences, which exist in the climates of South Africa. Both the annual and diurnal temperature ranges increase with distance from the sea, with altitude, situation and with dryness of the atmosphere. The differences between the mean temperature of the hottest and coolest months is 12° at Durban, 15.8° at Pieter maritzburg, and 25.6° at Kimberley, which is 34o m. from the coast, and over 4,000 ft. above sea-level. A range of 25° shows the effect of local situation at Weenen, which is only 8o m. from the sea, and 2,84o ft. in altitude, but which is situated in a large, saucer-shaped hollow. Places in the Karroo also experience great
ranges of temperature, because of the intense dryness of the at mosphere. The diurnal range is a very marked feature of the climate of South Africa, particularly inland. Sudden falls of tem perature often take place at sunset, especially in the dry season.
They may also be caused by a sudden change in the direction of the wind. Extremes of temperature are liable to occur. In the summer months the thermometer may rise to over roo°, even at places more than 4,000 ft. above sea-level. Cases of sunstroke are curiously rare, even though no special precautions, such as the use of pith helmets, may be taken to guard against it. Apart from the lower regions of the north-east Transvaal, parts of Zululand and a narrow belt of country along the coasts, the whole of South Africa is liable to frosts, though the number of these, and their severity, vary from one district to another. Ground frosts may occur in the Karroo, even in summer.
The rainfall is very variable both in the seasonal amount, and in the time at which it falls. In general it decreases from east to west. Durban receives a little over 4o in. per annum, Ladysmith 27.31, Prieska 9.75 and Port Nolloth 2.57 inches. Topographical features, of course, produce local variations. In Natal the edges of escarpments facing the sea often form well-marked mist belts in the summer months. In the Cape Province the contrast be tween two flanks of a mountain range is often very sharp. For instance, George has a rainfall of 34.36 in., while Ezeljagt, 12 m.
away, but on the landward side of the Outeniqua range, has only 14.98 inches. The highest rainfall, so far recorded, occurs in the mountains near Paarl, where several stations receive about 200 inches. This, however, only applies to a small area, and is not representative of South African conditions. In the Cape Province, out of a total area of 276,966 sq.m., 177,677 have a rainfall of from 5 to 15 in. per annum. In the Orange Free State, the total area of which is 50,389 sq.m., 32,66o receive 15-25 inches. In the Transvaal, 70,764 sq.m., out of a total of 110,450, have an annual rainfall of 15-25 inches. In Natal, 21,231 sq.m. out of a total of receive 25-35 inches, while a further 14,060 sq.m. have an annual amount of 35-50 inches.