The main cooling influence is the cold north-flowing Benguela current from the South Pole, and it mingles with the warmer Agulhas current from the Indian Ocean lowering water temperatures between Cape Town and Cape Agulhas. The large difference in temperature between the ocean and the land causes regular beneficial coastal fog and cooling breezes. Rain falls mainly between May and August. In the north of the Western Cape it is reduced due to the decrease in the impact of the Benguela current and mountain protection along the coast line. Irrigation or old vines therefore essential in the drier areas.