"I feel amazing. Definitely woke me up," said first-timer Madi Wright of the experience.
"You kind of feel like you're going to die, but it's okay and then you're just ready to roll," added repeat participant Lydia Pond, who drives downtown from Plainfield every year to make a splash.
While many jump in the lake for the thrills, some take on the challenge for charity.
Aly Parson raised $300 for Dare2tri, a non-for-profit supporting paratriatheletes, and promised to run into the frigid water in return.
"Now that I've done it, I really feel rejuvenated," she said.
In Waukegan, everyone participating in the 20th-annual Polar Bear Plunge was supporting "Special Recreation Services of Northern Lake County (SRSNLC), helping individuals with disabilities participate in camps, athletics, health and fitness programs, and much more," according to the event's website.
There are certainly people who won't even dip their toes in to that water. But they were out on North Avenue Beach as well, "so I can take the pictures of my crazy family," as Donna Van Buskirk explained.
When asked if he'd join his parents in the future, 9-year-old Oliver Eltink said "nope... it looks too crazy."