After months of indications that it was coming, infamous climate agitator El Niño formed this week, climate scientists announced Thursday.

"Weak El Niño conditions are present and are expected to continue through the spring," the Climate Prediction Center said.

El Niño is a periodic natural warming of seawater in the tropical Pacific. It is among the biggest influences on weather and climate in the United States and around the world.

It typically brings unusually wet weather across the USA's southern tier, according to Mike Halpert, deputy director of the prediction center. The weather this winter has generally had an El Niño flavor to it, he said, even though it hadn't officially formed.

Storms that slammed into the West Coast this week could be related to El Niño, but that's far from certain. This week's storms are courtesy of an "atmospheric river" that funnels water vapor from the tropics to the West.

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Halpert said the forecast for the next few weeks is for wet weather across the nation, part of which could be chalked up to this El Niño.

Otherwise, looking ahead, forecasters said Thursday that "due to the expected weak strength, widespread or significant global impacts are not anticipated."

Officially, federal forecasters said there's no reliable way to predict what El Niños might mean for the spring thunderstorm and tornado season. Research in 2016 by the National Oceanic and Atmospheric Administration, however, showed that a weak, fading El Niño increases the probability for tornado outbreaks in the Upper Midwest in May. A study published in 2015 in the British journal Nature Geoscience indicated it brings a quieter tornado season in the Southeast.

As for hurricanes, although this El Niño may not last through the summer, El Niños often tend to suppress the number of hurricanes that form in the Atlantic.

El Niños tend to increase hurricane activity in the eastern Pacific Ocean, which can affect Mexico, the U.S. Southwest and Hawaii. Federal forecasters make seasonal hurricane predictions in late May, so it's too early for a definitive forecast, Halpert said.

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During an El Niño, water temperatures in the central and eastern tropical Pacific Ocean get a few degrees warmer than average, typically at least three to five months.

Though the ocean had warmed to El Niño levels over the past few months, the atmosphere had yet to respond to that warming, which prompts the official designation. It has now.