El Niño Could Mean A Milder Chicago Winter. But Keep Your Snow Shovel Handy

CHICAGO — While Chicagoans won’t receive a “refund” for a wet and “miserable” summer, the city could be in line for a warmer-than-usual fall and winter.

That would be thanks to an El Niño that forecasters say could become the strongest on record. 

El Niño is a climate pattern that occurs when surface water temperatures in the central and eastern Pacific Ocean are warmer than average. It causes the Pacific jet stream to move south of its neutral position, leading to drier and warmer conditions in the northern U.S., according to the National Oceanic and Atmospheric Administration.

NOAA’s Climate Prediction Center gives a greater than 90% chance of a “very strong” El Niño throughout fall and winter, and a 69% chance during October through December of “a historic event” that would be stronger than any other El Niño events dating back to 1950.

Chicago falls in an area with a 40% to 50% chance of above-normal temperatures for the meteorological winter, which is from December through February, according to NOAA. The city’s average winter temperature is about 28 degrees.

That doesn’t mean Chicago is off the hook for snow and bouts of bitter cold.

“The fact that we’re milder overall during El Niño winters does not mean we’re not going to get snow. It does not mean we’re not going to get severe winter storms and winter weather,” said Illinois state climatologist Trent Ford. “There tends to be a little bit less snowfall, but it’s not always the case. We have a handful of years where we actually get well above average snowfall during El Niño years.”

That’s because above-average temperatures in January and early February mean more time around the freezing point, which can actually produce more snow, Ford said.

El Niño shifts the odds for certain climate patterns, but it does not necessarily determine the weather for an entire season. NOAA notes that El Niño’s typical U.S. impacts are common, but not guaranteed, and individual weather events still vary. 

“There are a lot of other things that can influence our winter climate, including what’s going in the Arctic, what’s going on in the north Pacific and the Atlantic,” Ford said. “All of those things matter, but, in general when we have such a strong El Niño, it usually tends to take control and give us a bit of a milder winter overall.”

While El Niño can favor drier conditions, NOAA is not predicting an unusually dry or wet winter for Chicago. Its precipitation outlook gives the city equal chances of above, near or below average precipitation. Chicago’s average winter precipitation is about 6 inches, while its average winter snowfall is nearly 30 inches.

A milder winter doesn’t necessarily mean Chicagoans will experience a less intense winter.

Scientists may use three-month average temperatures to describe a winter climatologically speaking, he said, “but that’s not how people experience winter.”

Chicago winters typically bring prolonged periods of cold weather, broken up by shorter stretches of milder temperatures and only occasional bouts of intense cold, Ford said. 

“Chicago winters tend to get this really bad rap, when in reality the majority of the time in the wintertime it’s not that bad. And then we get the really bad weather, but they’re short periods of time,” Ford said. “The way people experience winter is through that winter weather — the day, two days, three days where we get pretty cold temperatures, maybe some snow.”

The milder winter forecast in Chicago is just one piece of El Niño’s broader impacts.

“The milder winter does tend to be the biggest impact that it has here in the Midwest, but in other parts of the country and other parts of the world, they can see much more significant, in some cases negative, types of impacts,” Ford said.

El Niño can contribute to hot, dry conditions and increased risk of wildfires in Australia, for example, and parts of the western U.S. could see heavy rain and flooding, he said.

“Some folks may see the oft-reporting about El Niño and think warmer winter; that sounds great, what’s the big deal?” Ford said. “In reality, when we zoom out from Chicago, it can really affect the global economy, trade, livelihoods across the country and across the globe.”

______________________________________________________________________

Support Local News!

Subscribe to Block Club Chicago, an independent, 501(c)(3), journalist-run newsroom. Every dime we make funds reporting from Chicago’s neighborhoods. Already subscribe? Click here to gift a subscription, or you can support Block Club with a tax-deductible donation.

Listen to the Block Club Chicago podcast: