The Northeast is heavily influenced by the El Niño phenomenon and by the surface temperatures of the Atlantic Ocean.[13] El Niño years are characterized by below-average rainfall in the semiarid zone, which typically averages at 800 mm annually but is concentrated in a brief time period sometimes shorter than two months. During extreme droughts, precipitation can decrease by more than 50%.[13] As a direct consequence of variation in climatic patterns around the world in 1877 parts of Ceará witnessed four days of rainfall from March 18 to March 21. These rains allowed seeds to germinate, but it wasn't enough to sustain agriculture and cattle herds.