During heat waves like the one now baking the suburbs, hundreds of people flock to local lakes for a bit of cooling refreshment.
But can the water get too hot for comfort?
The blistering temperatures of the past week have boosted temperatures in suburban lakes, too. In McHenry County, water temperatures in some lakes have pushed well into the 80s, officials said.
"It can feel almost like bath water now," said Gail Weber, laboratory coordinator for the McHenry County Health Department. "When the swimming season began in late May, our lakes were in the high 60s to low 70s."
The higher-than-usual temps are also being felt in the area's biggest body of water, Lake Michigan. At Waukegan Beach in Lake County, water temperature reached a high of 76 degrees on Wednesday afternoon. In Chicago, the lake has been as warm as 78 degrees this week.
Over the past 20 years, the average temperature of Lake Michigan at this time of year is about 70 degrees, according to the National Oceanic and Atmospheric Administration.
Man-made swimming areas are feeling the heat, too. The water at Centennial Beach in Naperville, created on the site of an old quarry, was 81 degrees on Thursday, said the Naperville Park District.
In a week when air temperature has climbed into the mid-90s, though, few are complaining about warmer lake water.
"It's refreshing," Lake Barrington resident Patty MacCarthy said while enjoying a dip in Lake Zurich. "It's perfect for the grandkids because they just walk in without saying it's cold."
Lester Murin agreed the water's "just right."
"You can go in with no shock," the Lake Zurich resident said.
Suburban health officials say warmer water alone generally doesn't pose a health risk to animals or people. But when rising temps come after heavy rains, issues can arise, like an increase in algae.
Health officials say local lakes have had more algae blooms than usual.
"We have noticed it," said Mike Adams, a senior biologist with the Lakes Management Unit of the Lake County Health Department. "All the rain we've gotten has washed nutrients into the water. When mixed with the current heat, it creates algae blooms."
Algae is often harmless, but the "blue-green" type can make people and animals sick. Adams said the county routinely monitors lakes for large algae blooms and then tests those for the presence of toxins.
The combination of heavy rain and warm air can also lead to an increase in bacteria levels in lake water, which health officials monitor regularly. No dramatic spikes in bacterial levels have been observed, officials said.
So local lakes, despite the warmer water, remain a good way for sweltering suburbanites to beat the heat.
"It's very comfortable," Lake in the Hills resident Jennifer Bruns said on Thursday while relaxing in Woods Creek Lake with her mother, Dorothy Young. "It really doesn't feel as hot as it is."
Young laughed and added, "It's doin' the job."
• Daily Herald staff writers Laura Stoecker and Steve Lundy contributed to this article.