ascension has a hot desert climate ("bwh", according to the köppen climate classification). the temperatures at the coast average from , and about 5 to 6 °c (41 to 43 °f) cooler at the highest point. rain showers may occur at any time during the year, but tend to be heavier between june and september. although the island is in the tropical zone, average annual rainfall is very low. the cause of this might be the relatively low temperature of the ocean water, as the benguela current and south equatorial current flow northward west of africa. these currents bring cooling effects around the eastern south atlantic ocean. tropical cyclones also occur only rarely in the south atlantic ocean which might be caused by the same phenomenon, and by strong vertical wind shear.