In the parks, at the lakefront and beyond, swarms of mosquitoes, flies and other bugs are chasing away Chicagoans trying to enjoy the last breaths of summer. More so than in previous years, insects have been pervasive — and it’s no coincidence why.
Bugs, mosquitoes in particular, thrive and breed in hot, wet conditions, which is exactly the climate that Chicagoland has had this summer. According to National Weather Service data, 2026 marked the 17th-wettest summer since 1871.
Uptown residents Agnieszka Romek and her husband, Andrezej, always come to the same spot at Montrose Beach: a large rock toward the back of the beach that they sit on together, slightly tucked away into the brush. Their view ahead is the expansive sandy beach with Lake Michigan beyond.
On Thursday afternoon, their spot was also inhabited by small black and striped insects flying about the vegetation that the couple was forced to swat away. When the bugs landed on their skin, it left a faint stinging sensation. Romek said she had never seen this many bugs at the beach before.
“We are here every week,” Romek said. “It was never like this.”
As Labor Day approaches, the pesky pests, including cicadas that seem to be extra loud this year, threaten to upend backyard barbecues and lakefront beach parties with their buzzing invasions.
Warmer, wetter summer leads to more bugs
The heavy rains Chicago saw this summer could have led to a higher presence of swarming insects, as flies and mosquitoes both prefer to breed near pools of still water, according to Chris Dietrich, a University of Illinois entomologist.
“Anywhere where even a little bit of standing water is accumulating, that’s an ideal site for a female mosquito to go and lay some eggs in there and have the larvae develop,” Dietrich said.
Additionally, bugs tend to breed more often in warmer temperatures, said Dietrich. Faster life cycles directly correlate to a multiplication of mosquitoes. He called this summer’s conditions “ideal” for flies and mosquitoes.
“Their populations tend to fluctuate pretty dramatically from year to year in response to climatic conditions,” Dietrich said. “We’ve had a pretty warm, wet summer so far. Those warm, humid conditions seem to be very good for promoting growth and the expansion of insect populations.”
While it’s not unusual for Chicagoland to have a rainy summer, this much rain is abnormal for the region, according to Kevin Donofrio, science and operations officer at the National Weather Service. From June 1 through Sept. 1, Chicago saw 15.38 inches of rain, which is 3.32 inches above average.
Flies visit at a water fountain near Tobey Prinz Beach Park in Chicago’s Rogers Park neighborhood on Sept. 3, 2026. (Arthur Maiorella/Chicago Tribune)
There were also 46 different flash flood warnings issued within the city of Chicago during that same period. The warnings were issued on 15 separate dates.
“It was truly a wet summer,” Donofrio said.
Chris Anchor, chief wildlife biologist at the Forest Preserves of Cook County, said that in the last six to 10 days, the bugs have been particularly pervasive.
“We went through that period of drought and the bug population was greatly diminished,” Anchor said. “When that precipitation hit the ground, the conditions became correct, and we had a huge hatch of many different types of insects.”
Urban Rivers field operations manager Stephen Meyer, right, and intern Caitlin Prescott collect a sampler to study the ecosystem in the North Branch of the Chicago River on Sept. 3, 2026. “My theory was that some of the (flying insects) spike had to do with the swallows migrating away,” Meyer said. “Especially at the Wild Mile we have a lot of swallow nests, cliff swallows and barn swallows, all over the Halsted Bridge, real close by and they seem to keep the flying insects in check most of the year. But they left a couple weeks ago, and last week we just got inundated with all these flying insects. That does happen every year, but this year has been particularly bad.” (Eileen T. Meslar/Chicago Tribune)
No events at the forest preserves or the Chicago Park District have been canceled due to the buggy conditions. Park District spokesperson Michele Lemons said the Park District has not received any influx of concerns regarding the presence of mosquitoes and other insects.
Not only are the bugs annoying to folks spending time outdoors, but they also may carry West Nile virus, according to Anchor. At least 13 people have contracted the disease in Illinois this year, according to Illinois Department of Public Health data. The first West Nile virus-related death of 2026 in the state was announced Tuesday. In Aurora, two residents were hospitalized with the virus, the Kane County Health Department said Thursday.
Karen Franklin’s dog Stanley sits in her bike’s basket at the Montrose Beach Dog Friendly Area on Sept. 3, 2026, on Chicago’s North Side. Franklin described an army of flies attacking Stanley on Tuesday. (Arthur Maiorella/Chicago Tribune)
The bugs, some transmitting West Nile virus to white-tailed deer, crows and blue jays, have also caused animals to die, according to Anchor.
To protect humans spending time outdoors, mosquito traps have been installed at Chicago parks across the district, and the city Department of Public Health supplied larvicide to catch basins to prevent immature mosquitoes from developing, Lemons said.
When will the bugs disappear?
As to when the bugs will be done: The mosquitoes and flies will not be around for the long term. As temperatures begin to cool in the fall, the bugs will become less visible, said Dietrich. When temperatures dip into the 30s and 40s at night, insects will become scarce across Chicagoland. The city typically achieves these lows in mid- to late October, according to Donofrio.
The mosquitoes and flies will die off during the first hard frost of the year, which also typically lands in October, according to the weather service.
Until then, Anchor recommends that people spending time in the forest preserves or out in nature wear long sleeves, long pants and carry insect repellent to keep the bugs away.