The Pacific Ocean surface contributing to the El Niño that has roiled global weather patterns has begun to cool, and the entire phenomenon may fade completely by June, the U.S. Climate Prediction Center said.

It is too early to say if the El Niño is already waning, because while the water is cooler, the atmosphere's reaction to the Pacific temperatures, the other half of the phenomenon, is still quite strong.

Forecast models favor its atmospheric and oceanic components to wind down through the Northern Hemisphere spring and vanish by early summer, the center said. There's about a 40 percent chance a La Niña, marked by a cooling of the Pacific, may start gaining ground sometime between August and October.

"We saw some of our strongest atmospheric metrics so far in the past month, so I don't think it's very accurate to say the entire phenomenon is weakening," said Michelle L'Heureux, a meteorologist at the center in College Park, Maryland. "From the ocean perspective, it is definitely not a rapid weakening so far and we're still seeing a strong event."

This year's El Niño has been blamed for a spike in Pacific typhoons, choking smoke blanketing Singapore and droughts across Asia and southern Africa. In the U.S., it's implicated in a record warm December and heavy rains that have contributed to flooding on the Mississippi River.

The storms bringing high amounts of rain and snow are expected to persist across the southern U.S. through the rest of the winter. Northern states may end up being drier. El Niño's impact on the U.S. is greatest in January and February. Australia's Bureau of Meteorology said earlier this month that a number of indicators suggested El Niño had peaked.

Like El Niño, La Niña disrupts global weather patterns, typically increasing Atlantic hurricanes and tropical storms.