La Nina is the cool phase of the El Nino-Southern Oscillation, a naturally occurring global climate pattern that involves changes in wind and ocean temperatures in the Pacific and can cause extreme weather across the planet.

Forecasters are predicting a weak La Niña event for this winter. Here's what that means for weather in the US.

In general, La Niña brings colder than normal temperatures across western Europe. Forecasters are expecting that temperatures will drop on the continent as we head towards November and December.

Cooler than normal temperatures are common in the northwestern United States and Canada. Warmer than normal conditions are usually experienced in the southern and eastern United States. The jet stream (the path that storms take) usually dissects the Valley which can lead to big temperature swings.

There’s a high likelihood La Niña will affect the U.S. this winter, a weather pattern characterized by warmer, drier conditions across most southern states with increased precipitation and cooler conditions in other regions,

A weak La Niña is expected to develop ahead of the season and influence temperatures, precipitation, and by extension, even snow across the United States. La Niña is a natural climate pattern that influences global weather marked by cooler than average ocean temperatures in the equatorial Pacific.