Unless you’ve been hibernating with Punxsutawney Phil this winter, chances are that you know about El Niño, a periodic warming in surface ocean temperatures across the central and east-central equatorial Pacific Ocean, which has been altering weather across the globe. The effects have ranged from wildfire-causing droughts in Indonesia to ocean storms off the coast of Chile, with waves massive enough to rush up onto land and flip an SUV.

An El Niño’s effect on weather can be complex, and in some cases didn’t behave as predicted. In drought-ravaged California, for example, meteorologists thought the ocean temperature phenomenon probably would bring above-average rain to the southern part of the state in January, with a lesser chance of precipitation in the north.

Instead, the opposite happened — southern California stayed pretty much bone dry with just three days of rainfall, while northern California got the coveted rain and snow in the mountains.

PHOTOS: El Nino Fuels Wild Weather

But in any case, it’s time to start bidding farewell to El Niño. The National Oceanic and Atmospheric Administration’s latest status report notes that while still strong, it’s on the wane, and by May or June, temperatures should be back to the norm.

In fact, NOAA says there’s a possibility that during the fall, we may actually see Pacific Ocean temperatures swing in the other direction, so that we get an La Niña — that is, an unusually cold east-central Equatorial Pacific.

NEWS: Why El Nino Didn’t Solve California’s Drought

La Niña tends to bring nearly opposite effects of El Niño to the United States. According to the Weather Channel, that could mean that the Pacific Northwest and Ohio Valley will be wetter than average, while the southern part of the United States will be drier. Temperature-wise, an area stretching from the Pacific Northwest to the northern Plains will be cooler than usual, while the South, the Ohio Valley an the mid-Atlantic states will see above-average temperatures.

While La Niña doesn’t occur as often as El Niño, it often lasts longer, persisting or occurring for two or more years.The most recent La Niña was a relatively weak event in 2011-12. Here’s a historical chart.