The eastern, equatorial Pacific Ocean is currently experiencing cooler than average temperatures, otherwise known as the La Niña phase of the El Niño Southern Oscillation.
The World Meteorological Organization is forecasting La Niña to continue into the third, consecutive winter which would make it a "triple dip."
Each phase of La Niña - or its opposite, El Niño - typically lasts between nine months and a year, making this the first "triple dip" La Niña of the last century.
Under normal circumstances, a prevailing wind known as the "trade winds" flows from east to west near the Equator.
The wind pushes warmer water from off the coast of South America to near Asia.
During a La Niña year, the trade winds are especially strong, pushing the warmer water further east and causing upwelling - a process that causes cooler water to rise to the surface.
That cooler-than-normal water affects global climate patterns.
During a typical wintertime La Niña, the Pacific Northwest tends to experience cooler than normal temperatures and above normal precipitation.
In Montana, a La Niña is preferred, as the El Niño generally brings warmer temperatures, dry conditions, and a worsening drought.
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