Chicago broke a record more than a century old for the warmest daily temperature recorded on Oct. 29, according to the National Weather Service.
Temperatures climbed to 82 degrees at O’Hare Airport Tuesday, topping the previous daily record of 78 degrees. Mark Ratzer, a meteorologist in the weather service’s Chicago office, said that the record had stood since 1901, though it was also matched on Oct. 29, 1999.
The Chicago area has experienced what weather service senior meteorologist Gino Izzi called “a pretty unprecedented warm spell” since Monday. The warm weather is forecast to continue through Wednesday evening before temperatures will dip in time for trick-or-treaters Thursday.
Chicago also appears to be on track to see the warmest recorded low temperature for Oct. 29, though Ratzer said they won’t know for sure if that record has toppled until the climate day ends at 1 a.m. Wednesday. He said the record high minimum temperature for the day is 64 degrees, set in 1946.
The immediate cause of Tuesday’s heat was “strong southwesterly winds across the plans and Great Lakes,” Ratzer said.
But autumn temperatures have been climbing for years. According to climate scientists, fall temperatures have warmed by 2.5 degrees on average across the United States since 1970. In Chicago, October nights have gotten hotter by 3 degrees in the same timespan — from 42 to 45 degrees — which is consistent with an average 3.3-degree increase in nighttime temperatures across 216 U.S. cities.
Normal average temperatures for this time of year in the area have historically remained between 48 and 49, and the normal maximum is 56 to 57.
