Illinois officials are warning people who plan to recreate in lakes and rivers to be cautious about blue-green algae that can cause sickness or other health issues.
The Illinois Environmental Protection Agency and Department of Public Health say water conditions are ideal for the algae growth.
Rapid growth of the algae, known as a "bloom," can produce toxic chemicals that may make people and pets sick. Young children, the elderly and people with compromised immune systems are especially at risk. Symptoms include rashes, vomiting, diarrhea and wheezing.
Officials say people should avoid contact with water that is discolored, has green-colored streaks, looks like spilled paint or has surface scums or greenish blobs beneath the surface.
Activities near the water, such as hiking or camping, aren't affected.