cold snap expected Monday, warmer temps to follow


With beach season underway, meteorologists are urging Chicagoans to “stay dry when waves are high” as afternoon gusty winds and cooler evening temps Sunday result in dangerous swimming conditions along the lakefront until late Monday.

Despite mid-afternoon high temperatures and sunny skies to close out the weekend, a fast-approaching cold front can change beach conditions quickly.

“We are going to see waves increase really fast behind the front and that is why we are concerned about beachgoers, because they can be caught unprepared,” said Brett Borchardt, a senior meteorologist with the Chicago office of the National Weather Service.

Waves of 5 to 8 feet and life-threatening currents persisting into Monday evening will create a high swim risk on southern Lake Michigan beaches from Illinois to Indiana, which account for half of all drownings in the lake. The weather service also cautions people against venturing out onto piers, jetties, break walls and other shoreline structures.

In keeping with a beach hazards statement, in effect from 9 p.m. Sunday until 1 a.m. Tuesday, the Chicago Park District has asked visitors to keep an eye out on the flag color warning system, which is updated on their website at and each beach throughout the day. A green flag indicates swimming is permitted, a yellow one urges caution and a red flag means a swim ban is in place due to unsafe swimming standards.

Cool, breezy conditions will continue throughout Monday too.

“(It) will be the coolest day of the week and potentially one of the coolest days of the summer, if I go as far as to say that, with high temperatures along the lakeshore struggling to climb out of the low to mid-60s,” Borchardt said.

“But it is going to be a short-lived cold snap — if I may call it a cold snap — with temperatures quickly rebounding,” he said.

Temperatures will climb back to seasonably summer standards Tuesday through the second half of the work week, as they reach the mid- to upper-80s Wednesday. But the mild, pleasant weather could be interrupted by chances for thunderstorms and showers later in the week.

“We’re getting to the time of year where some of those storms could be strong to severe just given the amount of heat and moisture available in the atmosphere,” Borchardt said. “So it’s that Thursday to Friday timeframe we have our eye on right now for the highest chances.”

Beachgoers spend part of their afternoon at Oak Street Beach on May 21, 2024, in Chicago. (John J. Kim/Chicago Tribune)
Beachgoers spend part of their afternoon at Oak Street Beach on May 21, 2024, in Chicago. (John J. Kim/Chicago Tribune)

The meteorologist added that locals should keep in mind June and July are typically the hottest months of the year.

“Heat can sneak up on us, especially when we’re not acclimated,” he said. “So just keep an eye on friends and family.”

Last summer, the city was hit by waves of boiling-hot temperatures. In late July, heat indexes ranged from 95 to 105 degrees — a measure of relative humidity and air temperature that indicates how it really feels outside.

On Aug. 24, 2023, temperatures at O’Hare International Airport, the city’s official recording site, reached 100 degrees, the first time since the deadly heat wave of July 1995. Heat indexes then reached over 115 degrees.

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