Chicago facing last week of warm weather before temperature drops
The week leading up to Halloween will likely be the last with highs in the 70s before weather patterns turn colder and stormier.
On Sunday, O’Hare International Airport recorded a high of 73 degrees, according to the National Weather Service. This is below the record of 79 set on Oct. 25 in 1963. The normal high this time of year is 59.
Forecasts predicted highs would remain in the 60s and 70s over the next five days, potentially peaking at 79 degrees on Thursday, according to the weather service.
“It has been an unseasonably mild stretch, and what is driving this pattern is we had a series of high-pressure systems moving through the Great Lakes, and high-pressure systems typically give us tranquil patterns,” said Brett Borchardt, senior meteorologist at the weather service.
On Oct. 12, Chicago broke a daily record of 88 degrees set in 2008. Experts say there’s a strong chance of a mild winter as the world faces what could be the strongest-ever El Niño, a weather phenomenon involving warming in the Pacific Ocean.
Borchardt said this October is the sixth warmest on record for the area. However, temperature changes over the rest of the month could change its placement.
The warmer weather is expected to continue until Oct. 31, Borchardt said, after which temperatures will drop and the Chicago area will transition into a rainier, stormier pattern. Even once it gets colder, he said there are no opportunities for snow in the next two to three weeks.
“Typically we see our first snowflakes on Halloween; there are no signs of that this year,” Borchardt said.
The weather service won’t be able to make specific predictions on Halloween weather until Wednesday at the earliest, he said.
Trends in recent decades point to an overall warming of average temperatures in winter as well as fall, spring and summer, from human activities such as fossil-fuel burning that release heat-trapping gases into the atmosphere.
In Chicago, fall is the second fastest-warming season after winter, according to climate science nonprofit Climate Central.
fbelleau@chicagotribune.com