A cold Atlantic current produces an arid atmosphere around the archipelago. December–June is cool and dry, with temperatures at sea level averaging ; July–November is warm and dry, with temperatures averaging . Although some rain comes during the latter season, rainfall is sparse overall and very erratic. Accumulations are generally around annually in the northern islands and 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.