A ‘historically’ strong El Niño is expected to make for a milder Chicago winter

A potentially “historically strong” El Niño will make for milder winter temperatures in Chicago, according to the National Weather Service’s winter outlook report released Thursday.

An El Niño is a weather event that occurs when abnormally warm water temperatures in the Pacific lead to changes in weather patterns globally, specifically warmer temperatures across northern North America.

They typically occur every two to seven years. The last was in 2023 into 2024, and the current one has the potential to extend into March 2027.

“It’s probably just going to feel like any other warmer winter, especially for the latter half of the winter when the effect seems to be maximized,” said Kevin Doom, a meteorologist with the weather service. “That doesn’t mean every day will be above average though. We’ll still see periods of harsh cold and wintry precipitation events.”

For the Chicago area, that means a 50% to 60% chance of above-normal temperatures this winter, though the weather service said even in a mild winter to expect “notable” stretches of cold weather and snowstorms.

The predicted El Niño is expected to compete with the one from the winter of 1982-83 — which raised the average winter temperature for the area by 5 degrees to 7 degrees and lowered snowfall by 25% to 50% — for the strongest El Niño since 1950, according to the weather service.

The report also states the weather will make for a stronger jet stream, which should largely keep polar air, the cause of polar vortexes that bring brutal stretches of chilling cold, to a minimum.

However, the report notes that “no two El Niños are alike and impacts vary.”

“It’s not a guarantee, but given this one is overly strong, confidence is pretty high [we’ll see higher temperatures],” Doom said. “This is the strongest El Niño we’ve seen in a while, at least as long as I’ve been around.”