The Atacama Desert coast is subject to a climate of extreme aridity, and therefore generates a low average annual rainfall of (1970–2000), and the Town of Antofagasta itself receives an annual average of less than of rainfall per year, earning it the record as the world's driest town. However, the sporadic occurrence of heavy rainfall, together with the geomorphologic situation of the city, make it susceptible to be affected by mud flows and landslides. Between 1916 and 1999, the city was affected by floods or landslides on seven occasions: 1925, 1930, twice in 1940, 1982, 1987 and 1991, of which the most important episodes in 1940 and 1991.