"They've been biting me a lot," said 8-year-old Josiah Gonzales, who wanted to play basketball with his dad in Grafton before the mosquitoes got too bad.
"I'd say it's actually worse though than usual," he added.
Elena Bopa brought her kids to the playground but was ready to leave about 10 minutes later.
"I wouldn't think there are so many here right now, we didn't prepare," she said.
Heavy rains in late August have led to standing water in many places, which is the perfect breeding ground for mosquitoes.
Until all of the water dries up, the Department of Health Services recommends wearing bug spray, emptying containers around your home that collect water, and cutting weeds or vegetation where mosquitoes can hide.
"We couldn't even play basketball, they've just been attacking us," said Olaf Jurenko, who lives in Cedarburg. "It's been pretty brutal out here."
There has been one confirmed human case of West Nile Virus so far this year in Wisconsin. That's compared to 51 cases last year, which was the highest number since 2012.