The warmest days in summer are brought by the hot, dry air drawn out from the Sahara desert. This air may sometimes be ladened with fine dust particles (la calima) blown from the desert. However, by the time it reaches the islands the temperatures are lower with a higher relative humidity picked up during its passage across the cool ocean water. Some fog and cloud may occur at this time, but summers are generally dry and sunny with no extreme heat. The northern shores of the islands, being more exposed to the predominant northeast trade winds, are somewhat wetter than the sheltered southern coasts.