Altitude and Temperature
In South Africa, the lowest temperatures are usually found in the high-altitude areas and mountains, but this can be influenced by other factors.
If all other factors are equal, air temperature decreases with increasing height above sea level; i.e. the temperature goes down, as you go higher. An average of -6.5ºC per 1 000 m rise in altitude is often regarded as ‘standard’. Values ranging from as low as -4.6ºC to as high as 9ºC per 1000 m rise in altitude have been recorded at different places in the world.
Ocean Currents and Temperature
Comparing the average air temperatures along the east and west coasts of South Africa, you will notice the effect of the ocean currents on air temperature.
The average air temperature for Durban on the east coast is 21ºC while the temperature of Port Nolloth on the west coast is 14.2ºC. Both places lay approximately on the same latitude.
The east coast is influenced by the warm Mozambique current, a tributary of the Agulhas current, while the cold Benguela current decreases the temperatures along the west coast of South Africa.
Slope and Temperature
The slope aspect has a large impact on daily average temperatures especially in areas with low mountains and steeply undulating hills. In South Africa, north-facing middle slopes have higher temperatures than south-facing slopes.Temperature and Cloud Cover
In tropical areas, cloud cover affects long term seasonal temperature trends. Rainfall acts as a co-factor. The general trend is that the highest average temperatures in an area occur before the summer rains start. Such areas have a cool dry winter, a hot dry spring and a warm wet summer.
In the tropical area of northern Limpopo, the high temperatures and dry air in September and early October have severe negative effects on tea grown in the area. This is an important factor to consider when growing other crops under irrigation in that area.
Temperature and Wind
In South Africa, different winds have quite drastic effects on air temperature. The most important of these are the scorching hot, extremely dry ‘berg winds’, which blow from the hot, dry interior plateau down the escarpment onto the coastal plateaux during summer.
West coast areas like the Olifants River Valley, Vredendal, and the Eastern Cape coastal areas are probably the worst hit by berg winds. The irrigated areas in the river valleys of the Eastern Cape are also influenced strongly by berg winds.
During winter months, the central interior of the country, especially the Free State, is periodically hit by biting cold winds. These icy winds come from the south to south-east when it has snowed on the mountains of the Eastern Cape and Lesotho.
Source Water Research Commission