The abnormal warming had been present on the coasts of Peru since June 2016,[3] however, in agreement with the Peruvian studies, it is considered that the Coastal Niño event officially lasted from December 2016 until May 2017.

The strong rains originated due to the warming of the ocean that borders the Pacific coasts of Peru and Ecuador, a phenomenon referred to as the Coastal Niño.

As they passed by the coasts of Ecuador and Peru, the warm water currents didn't encounter a sufficiently strong trade wind barrier that could prevent their forceful arrival.

[5] The warm water is characterized to be superficial and to evaporate easily; it also increases temperatures to 29 degrees Celsius which generates an unstable atmosphere and constant rain.

This event would have been a Coastal Niño due to the fact that it was a phenomenon that in a localized manner largely affected the Peruvian coast, but without a larger influence on the global climate it probably would not be related to the weather pattern referred to as ENSO, (El Niño-Southern Oscillation).

Coastal Manabí declared a state emergency and the country's largest city, Guayaquil in Guayas experienced abnormally high rain events.

[15] Higher elevation regions including Quito experienced severe rains, landslides, and sinkholes towards the tail end of the Coastal Niño event as the ITCZ began moving north towards its more usual latitude.

[22] In Piura, 300 mm (12 in) of rain fell in one day, three times the city's annual average and Catacaos had flood waters rise to 1.8 m (5.9 ft) high.

In Brazil, Heavy rains on March 11–13, 2017, including 110 mm (4.3 in) in 24 hours, caused flooding across Rio Grande do Sul, killing 2 people, injuring 70, and leaving 10 others missing.

[25][26] From the beginning of the Coastal Niño, the Peruvian and Ecuadorian coasts have seen the effects of various disasters which have caused hundreds of fatalities and thousands of damages.

Torrential rains accompanied the thunderstorms that began in the regions of northern Peru such as Lambayeque, La libertad, and Piura as well as in the provinces of the south of Ecuador such as El oro, Lloja, and Azuay.

Other cities that are commonly rainy, like Quito and Riobamaba, recorded historic levels of precipitation 5 to 6 times greater than normal.

[28] The Ecuadorian city of Cuenca also recorded a strong hailstorm that paralyzed traffic and obliged the municipal authorities to declare a state of emergency suspending classes in schools, colleges and universities.

Virtually all of Peru and Ecuador experienced repeated flooding due to the overflow of rivers and ravines caused by the rain and the mudslides that easily transported water to them.