The 2015-2016 El Nino weather phenomenon, one of the most powerful on record, has begun its decline but continues to have a strong influence on global climate patterns, the UN's weather agency said Thursday.

The World Meteorological Organization (WMO) said El Nino, which occurs every two to seven years, has "passed its peak" but ocean temperature rises in recent months proved its considerable impact.

"We have just witnessed one of the most powerful ever El Nino events which caused extreme weather in countries on all continents and helped fuel record global heat in 2015," WMO Secretary General Petteri Taalas said in a statement.

The UN agency had forecast this El Nino to be the worst in 15 years, a prediction borne out by ocean temperatures recorded in late 2015 that were more than 2.0 degrees Celsius above average.

The WMO statement said this El Nino was comparable to the particularly strong phenomena recorded in 1982-83 and 1997-98.

"Parts of South America and East Africa are still recovering from torrential rains and flooding," the statement said, linking those events to El Nino, which sparks global climate extremes.

"The economic and human toll from drought...is becoming increasingly apparent in southern (Africa) and the Horn of Africa, central America and a number of other regions," it added.

This El Nino is expected to end towards the middle of the year.

While scientists say weather patterns like El Nino are not caused by climate change, rising ocean temperatures caused by global warming are believed to impact their intensity and frequency.