A cold Atlantic current produces an arid atmosphere around the archipelago. There are two seasons: December–June is cool and dry, with temperatures at sea level averaging 21° C (70° F ); July– November is warmer, with temperatures averaging 27° C (81° F ). Although some rain comes during the latter season, rainfall is sparse overall. Accumulations are generally around 13 cm (5 in) annually in the northern islands and 30 cm (12 in) in the south. The archipelago is subject to cyclical droughts; a devastating drought began in 1968 and was broken only briefly in 1975, 1978, 1984, and 1986.