It caused an estimated 16% of the world's reef systems to die, and temporarily warmed air temperature by 1.5 °C (2.7 °F) compared to the usual increase of 0.25 °C (0.45 °F) associated with El Niño events.

[3] It led to a severe outbreak of Rift Valley fever after extreme rainfall in north-eastern Kenya and southern Somalia.

[9] By September 1997, the ENSO became very powerful, with surface temperatures between South America and the International Dateline averaging 2–4 °C (3.6–7.2 °F) above normal, roughly a quarter of the planet's circumference.

Additionally, the band of warmth along the Pacific coast of North America continued to expand, now stretching from Alaska to southern Mexico.

However, the region of cooler than average water in the western Pacific expanded, signifying that a La Niña would take shape in the latter part of 1998.

[15][16] The area where most of the tropical cyclones developed was shifted eastwards, with parts of the Cook Islands and French Polynesia impacted as a result.