Owing to the increase in the height of the plateau towards the north-east, there is hardly any increase in temperature from south to north as might be expected. The third feature is the striking contrast between temperatures on the east and west coasts. Temperatures above 32oC are fairly common in summer, and frequently exceed 38oC in the lower Orange River valley and the Mpumalanga Lowveld. A record temperature of 48,8oC has been recorded at Vioolsdrif in the Northern Cape in January 1993. Frost, humidity and fog Frost often occurs on the interior plateau during cold, clear winter nights, with ice forming on still pools and in water pipes.
Frost decreases to the north, while the coast is virtually frost-free.
Average annual relative humidity readings show that, in general, the air is driest over the western interior and over the plateau. Along the coast, the humidity is much higher and at times may rise to 85 per cent. Low stratus clouds and fog frequently occur over the cool west coast, particularly during summer. The only other area that commonly experiences fog is in the 'mist belt' along the eastern foothills of the Escarpment. Sunshine South Africa is famous for its sunshine.