South Africa lies almost wholly within the southern temperate zone, and its climate is more equable than that of corresponding northern latitudes because of its surrounding waters. Temperature differentials between east and west coasts stem from the influences, respectively, of the warm Mozambique (Agulhas) Current and the cold Benguela Current. The average daily minimum temperature at Durban, on the east coast, ranges from 11° C (52° F ) in July to 21° C (70° F ) in February; on the west coast, at Port Nolloth, the range is from 7° C (45° F ) to 12° C (54° F ) during the corresponding months. Temperatures are cooler in the highlands: at Johannesburg, the average daily minimum is 4° C (39° F ) in June and July and 14° C (57° F ) in January. On the high veld there are sharp differences of temperature between day and night, but there is less daily fluctuation nearer the coast. Rainfall is unpredictable in large parts of the country, and prolonged droughts are a serious restriction on farming in such areas. While the mean annual rainfall is 46 cm (18 in), 21% of the country receives less than 20 cm (8 in) and 31% gets more than 60 cm (24 in). Much of South Africa gets its rain in the summer months, but the western coastal belt is a winter rain area. Along the Cape south coast, rain falls during both seasons.