A colder and wetter than average winter is in store for the Pacific Northwest, while the southern United States and California are expected to see a warmer and drier winter, government forecasters announced today (Oct. 21).

Overall, forecasters expect another winter of extremes ahead based on the strengthening La Niña, a climate phenomenon that is associated with cooler-than-normal water temperatures in the equatorial Pacific Ocean.

This includes increased chances of storms and flooding in the northern plains and the Ohio and Tennessee valleys, while drought conditions continue in Hawaii.

La Niña has the opposite effect as its cousin El Niño, but both occur every two to five years and drive extreme weather around the globe. Last winter's El Niño contributed to record-breaking precipitation and flooding in some parts of the United States, while other areas experienced record heat and drought. [ LIVE SCIENCE ]