Tuesday forecast: Highs in the mid 70s expected before storms roll in

Temperatures in Chicago climbed to more than 70 degrees Tuesday afternoon, putting the city on track to potentially break a decades-old record. But meteorologists warned that a “dramatic” cooldown along with thunderstorms, hail and damaging winds are on their way overnight.

David King, a meteorologist at the National Weather Service in Romeoville, said temperatures reached 73 degrees by 2 p.m. at O’Hare International Airport, the city’s official recording site. The daily record for Feb. 27 was in 1976, when temperatures topped out at 75 degrees, also marking the warmest day in the entire month of February on record.

“I think that the chances of it getting to 75 are fairly good,” King said. “Getting above that’s going to be the tricky part. The sun is out, there’s still warming that could happen. It’s plausible.”

Weather officials expect thunderstorms to start around 6 p.m. Tuesday, with “destructive” hail up to two inches in diameter. There’s a threat of winds up to 60 miles per hour and tornadoes in portions of north central and northeast Illinois, and northwest Indiana.

A “strong” El Niño and long-term warming due to climate change are the main causes of these above-average temperatures, according to Trent Ford, the Illinois state climatologist. El Niño is a natural climate phenomenon where sea surface temperatures are warmer than average in the central and eastern Pacific Ocean near the equator, according to the weather service.

Warming winter temperatures are also the most “substantial” and most “consistent” signal of climate change, Ford said. While temperatures like this year’s may not become the norm every winter, Ford said there’s a strong possibility they will become more frequent than in the past 1,500 years.

“No matter the model, no matter the scenario, everything all points to warmer winters,” Ford said. “We can’t say exactly how much this winter’s mild weather is due to climate change versus El Niño, but there is an important role that climate change is playing.”

But warm temperatures won’t last for long Tuesday due to a “really robust cold front,” King said. Less than half an inch of accumulating snow is possible late in the night, leading to potentially dangerous travel conditions Wednesday morning.

After midnight he said temperatures will plummet about 20 to 30 degrees in an hour with gusts of wind up to 45 miles per hour. There’s about a 30% chance of wind gusts above 50 miles per hour, officials said. By the morning, King said temperatures in the 20s are likely.

“That’s going to make for brutally cold wind chills as well,” he said. “That 6 a.m. it might be in the 20s from a temperature perspective, it’s going to feel like it’s in the single digits.”

There’s been a few records already broken this month, King said. The temperature Monday reached 71 degrees, becoming the warmest Feb. 26 on record. The previous record was 64 degrees in 2000. It was also the first above 70 degree day at O’Hare in February since 2017, King said. It’s possible that the month will also become the warmest February on record.

If warmer temperatures continue into March, Ford said an early start to spring is possible. He said he’s already seen some early-spring plants, including crocuses and daffodils, pop up in Champaign. Agricultural crops such as peaches, apples, cherries, pecans and walnuts also could break dormancy earlier than usual, leading to an increased risk of spring freeze damage, he said.