(Inside Science TV) -- You may remember El Niño events of years past. The weather phenomenon is back and in a big way, brewing in the Pacific and headed towards the U.S.
Major snowfall -- massive amounts of rain -- flash floods and droughts. The U.S. could see a little bit of everything this winter.
"This El Niño is going to be, and already is, a big one," said Daniel Swain, an earth systems scientist at Stanford University in California.
But what exactly is El Niño?
"El Niño is this periodic warming of the equatorial eastern Pacific Ocean that occurs roughly every two to seven years," explained Swain.
This year, the ocean is expected to warm by about five degrees Fahrenheit. It may not sound like too much but…
"That is about as high as we've ever observed," said Swain.
The higher temps and a shift in the jet stream will impact winter weather patterns across the country.
"There is an increased likelihood of a wetter than average winter in California," said Swain.
This may bring some much needed relief to the area suffering from a four-year drought…but too much rain could cause serious flooding.
"It's going to have some really major impacts not only in California but around the world."
And it's not just California that will be affected, this year's El Nino will impact weather systems around the world. In fact, some areas will actually get less rain and snow.
"The Pacific Northwest has a good chance of being drier than average, which is not great news for that part of the world because up there too, they are experiencing a drought."
States bordering Canada can expect warmer temps on average. But they will likely still see snow and have plenty of cold days.
You can certainly get big snow storms in an El Niño year and, it is in fact the case in some of the warmer years is when the bigger snow storms have actually occurred.
That means potentially good skiing conditions for the southern Rockies.
For the most part we will start to feel El Niño effects starting in December and running through March 2016. So in much of the U.S., you're going to get a visit from El Niño.