DuPage County, IL – The Forest Preserve District of DuPage County is warning visitors to keep dogs out of the water after an active harmful algal bloom was confirmed at the off-leash dog area within East Branch Forest Preserve.
According to the Forest Preserve District of DuPage County, the bloom was confirmed Monday, July 20, 2026, and warning signs have been posted while staff continue monitoring water conditions.
Officials said algal blooms are a common natural occurrence but can quickly become harmful during warm weather by producing toxins. Those toxins can make pets, children, and people with weakened immune systems sick if contaminated water is swallowed or inhaled.
The district noted that harmful algal blooms may appear as blue, green, or brown paint-like material floating on the water’s surface. Because it is not possible to determine whether a bloom is producing toxins simply by looking at it, officials recommend avoiding contact with any suspected bloom.
The Forest Preserve District is urging visitors to:
- Keep pets out of the water.
- Avoid touching the water or algae.
- Wash skin or fur thoroughly if contact occurs.
District staff will continue conducting visual inspections, and warning signs will remain in place until the bloom subsides.
More information about harmful algal blooms is available through the Forest Preserve District of DuPage County.
