Fall weather has arrived in Chicago and residents are preparing for a potentially colder, wetter winter due to the arrival of La Niña.

La Niña refers to the colder sea water off the coast of Peru that causes different weather activities for regions around the globe due to the jet stream. Typically, La Niña brings colder temperatures and more precipitation in the northern United States during the winter, while warmer and drier conditions are predicted in southern states.

The chance of La Niña occurring by the end of November is about 60% and could last through March, according to National Weather Service forecasts.

This year, La Niña is expected to be weaker than normal, making weather predictions difficult so far in advance, according to National Weather Service meteorologist Zachary Yack.

“If it's a little weaker, there's a chance it's atypical from that perspective. “It depends on how each storm approaches,” Yack said.

While La Niña often indicates colder weather in the Chicago area during the winter, this year's weaker pattern could lead to different impacts on temperature.

“We will likely get cold snaps, but we could also see above-average temperatures,” Yack said.

The Old Farmer's Almanac, a reference guide for farmers and gardeners, predicts that this year's winter could be mild in terms of temperature and precipitation across the U.S. – but due to La Niña combined with the southern variation of El Niño, the story of Chicago look different. said editor-in-chief Sarah Perrault.

“The polar vortex is kind of shifting, Chicago is actually quite different than the rest of the country,” Perrault said. “The rest of the country is getting warmer while Chicago is getting colder.”

The coldest periods for the Chicago area are expected to be early and late November, early December and late January to early February, the Almanac predicts.

According to the weather service's latest forecasts, much of the Midwest — including Chicago — has an equal chance of experiencing above- and below-average temperatures from December through February. The same forecasts indicate that the Chicago area has a higher than average chance of precipitation, but the Almanac's forecast calls for less snowfall and less precipitation overall in the winter.

The weaker La Niña could mean fewer storms throughout the winter, Yack said, but that can't be said for sure.

Yack said his advice to residents remains largely the same throughout Chicago's winter: follow the weather forecast and prepare for winter storms when they are expected.

Perrault said Chicagoans should stay prepared all season long.

“Everyone should just stay bundled up no matter what,” she said. “We say, 'Don't wait for a snowstorm to buy your sled.'”