Pedestrians walk through the Loop on Tuesday, when temperatures reached 74 degrees.
Tyler Pasciak LaRiviere/Sun-Times
Last month’s unusually balmy weather turned out to have set a record for the warmest February on record in Chicago.
The average daily temperature in February settled at 39.5 degrees, surpassing the previous record of 39 degrees set in 1882, according to the National Weather Service.
There were a few main contributors to the mild month, NWS meteorologist Rafal Ogorek said.
This year’s El Niño “was probably the largest driving factor,” he said. The natural climate phenomenon, which happens every two to seven years, causes warm sea surface temperatures in the eastern Pacific Ocean, leading to milder and drier winters in the Midwest.
Another reason for those two springlike stretches last month were storm systems passing northwest of Chicago.
“Usually when that happens, we have winds from the south that allow more air from the Gulf Coast to come up to the Midwest,” Ogorek said.
Another factor: it didn’t snow much, and “when you have snow on the ground, it tends to keep temperatures a lot cooler,” Ogorek said.
About 1.2 inches of snow was measured at O’Hare Airport throughout February — the 12th lowest amount for the month in Chicago, according to the weather service.
In place of more snow, the Chicago area endured severe thunderstorms, including at least 11 tornadoes, to cap the month.
Those twisters substantiate some research linking climate change to severe weather occurring farther north, and earlier in the the season. Illinois has had the second-most tornadoes so far this year, with 12, behind Florida’s 29, according to the weather service.
Chicago had a couple of extreme fluctuations in temperatures last month, most noticeably the record-high 71 degrees on Monday, a near record-high 74 degrees Tuesday — followed by a plummet to the 20s overnight on Wednesday.
Climate change also likely played a role in the warmth, but it’s “tough to quantify” the impact on a given month or year, Ogorek said. The extreme changes are mostly a result of the atmosphere continuously trying to maintain equilibrium, he added.
“When we had a record-warm stretch here at the end of the month, that kind of allowed for a deeper, stronger low-pressure system to develop and usually when that happens you get a sharp drop in temperatures behind that, and with the strong weather systems that also increases the likelihood of severe weather occurring,” Ogorek said.
While one month can’t indicate how the rest of a year’s weather will fare, February could still be a foreshadow of what’s to come for the Chicago area.
The first half of March is forecast to have above-average temperatures, starting in Chicago with a high of 71 degrees expected Sunday and a high in the 60s on Monday, the weather service said.
The weather service’s Climate Prediction Center also calls for a chance of “above-normal” temperatures this summer.