> El Niño is a climate pattern that naturally occurs every two to seven years when ocean surface temperatures warm in the eastern Pacific.
From the National Oceanic and Atmospheric Administration (NOAA)[2]:
> El Niño can affect our weather significantly. The warmer waters cause the Pacific jet stream to move south of its neutral position. With this shift, areas in the northern U.S. and Canada are dryer and warmer than usual. But in the U.S. Gulf Coast and Southeast, these periods are wetter than usual and have increased flooding.
> El Niño also has a strong effect on marine life off the Pacific coast. During normal conditions, upwelling brings water from the depths to the surface; this water is cold and nutrient rich. During El Niño, upwelling weakens or stops altogether. Without the nutrients from the deep, there are fewer phytoplankton off the coast. This affects fish that eat phytoplankton and, in turn, affects everything that eats fish. The warmer waters can also bring tropical species, like yellowtail and albacore tuna, into areas that are normally too cold.
As far as the Continental United States is concerned, this means the Northern half of the country will be warmer than usual, the Southern half of the country will be wetter than usual, and the Northeast in particular will be drier than usual.