An extended stretch of hot weather may lead to higher concentrations of blue-green algae in Minnesota lakes.
The algae gathers on the surface of the water and is known to kill dogs if they drink enough of it. It can also cause rashes and respiratory problems for people.
Pam Anderson, who works for the Minnesota Pollution Control Agency, says people should be aware of the potential for trouble.
"This is just the time of the year that people need to be area and keep an eye on kids and pets and make sure that they're not in water that doesn't look good," she says. "Our tagline is 'When in doubt, stay out.'"
Anderson says blue-green algae feeds off phosphorous and other nutrients that may run into water. People can protect lakes by minimizing yard or farm soil that enters waterways.