Fall weather has arrived in Chicago and residents are bracing for what could be a colder, wetter winter due to the arrival of La Niña.
La Niña refers to the colder ocean waters off the coast of Peru that spark different weather activity for regions around the globe through the jet stream. Typically, La Niña brings colder temperatures and more precipitation to winters in the northern U.S. while the southern states see warmer and drier forecasts.
La Niña has around a 60% chance of emerging through the end of November and could last until March, according to projections from the National Weather Service.
This year, La Niña is forecast to be weaker than normal, making weather predictions this far in advance tricky, according to National Weather Service meteorologist Zachary Yack.
“When it’s a little bit weaker, there’s a chance it would be untypical from that perspective, it depends on how every storm approaches,” Yack said.
While La Niña often indicates colder weather through the winter in the Chicago area, this year’s weaker pattern could lead to different effects on the temperature.
“We’ll probably get cold snaps, but we could have above-normal temperatures as well,” Yack said.
The Old Farmer’s Almanac, a reference guide for farmers and gardeners, predicts this year’s winter could be mild in terms of temperature and precipitation across the U.S. — but because of La Niña combined with the southern oscillation of El Niño, Chicago’s story may be different, managing editor Sarah Perrault said.
“The polar vortex kind of gets displaced, Chicago’s actually quite a bit different than the rest of the country,” Perrault said. “The rest of the country will be warmer while Chicago will be colder.”
The coldest periods for the Chicago area are expected to be early and late November, early December, and from late January into early February, the almanac predicts.
From December through February, much of the Midwest — including Chicago — has an equal chance of experiencing above-average and below-average temperatures, according to the weather service’s most recent predictions. The same predictions indicate the chance of precipitation leans above average in the Chicago area, but the almanac’s forecast expects less snowfall and overall precipitation throughout the winter.
The weaker La Niña could mean fewer storms throughout the winter, Yack said, but it’s impossible to say for sure.
Throughout any Chicago winter, Yack said his advice to residents stays mostly the same: Follow the forecast and prepare for winter storms when they’re expected.
Perrault said Chicagoans should stay prepared throughout the season.
“Everybody should just always stay bundled up no matter what,” she said. “We say ‘Don’t wait for a snowstorm to buy your sled.'”