Djibouti has either a hot semi-arid climate ("BSh") or a hot desert climate ("BWh"), although temperatures are much moderated at the high elevations. On the coastal seaboard, annual rainfall is less than 5 inches (131 mm); in the highlands, it is about 8 to 16 inches (200 to 400 mm). Although the coastal regions are hot and humid throughout the year, the hinterland is typically hot and dry. The climate conditions are highly variable within the country and vary locally by altitude. Summers are very humid along the coast but dry in the highlands. Heat waves are frequent. Annual precipitation amounts vary greatly from one year to another. In general, rain falls more frequently and extensively in the mountains. Sudden and brutal storms are also known to occur. Wadis turn for a few hours into raging torrents tearing everything in their path, and their course is regularized. Rainwater serves as an additional water supply for livestock and plants alongside seasonal watercourses. The highlands have temperate climate throughout out the year. The climate of most lowland zones is arid and semiarid.