If things are feeling weirdly warm for November, you’re not alone—places throughout North America are experiencing record high temperatures after an unseasonably warm October. But don’t ditch those unused winter coats and mittens just yet: As Eric Berger reports for Ars Technica, a weather phenomenon that all but guarantees a chilly winter.
It’s called La Niña, and it happens when the temperatures in the equatorial Pacific Ocean cool down. Though the phenomenon is associated with with a warmer than normal winter in the Southeast, the effect is the opposite for the Northwest, which tends to be cooler than normal during a La Niña year. And as Berger writes, the phenomenon was just confirmed by climate officials.
Right now, National Weather Service predictions show a weak La Niña sticking around through the winter, affecting both temperatures and precipitation. For northern parts of the United States, that means more precipitation and cooler temperatures than usual and the opposite in the southern half of the country.
Though wetter than normal conditions will soak places like the northern Rockies, drought conditions will likely persist in California, which is still parched despite a damp El Niño event earlier this year. The dry conditions will also worsen in places like the Deep South, which has been exceptionally dry this year. For the middle of the country, however, it could go either way.
Of course, La Niña patterns aren’t the only ones that dictate climate. In a media release about the U.S. winter outlook, NOAA notes that though the phenomenon is linked to heavier snowfall around the Great Lakes, snow forecasts aren’t possible without more data on developing storms. And other oscillations in atmospheric pressure and temperature in places like the Arctic and the tropics can influence how much precipitation is generated and how cold the weather gets.
Intense La Niña years can lead to severe droughts, as in 1988 when the phenomenon combined with other atmospheric anomalies to create the worst Great Plains drought since the Dust Bowl. But this year may be a lucky break. This latest La Niña appears to be relatively weak, which means that the ocean and parts of the atmosphere will get a much-needed cooldown before the next warmup.
There’s still plenty of uncertainty in the works: After all, weather is hard to predict and just a few months ago, climate experts claimed the phenomenon wouldn’t show up at all. It’s all just proof that, though Earth likes its cycles and patterns, there’s always an element of surprise hiding in the wings—just like that winter coat still hiding in your closet, for now.