Washington, D.C. – From Arizona to the Great Lakes, officials are warning holiday travelers to avoid scummy or discolored water this weekend as harmful algal blooms (HABs) spread across U.S. lakes and rivers during the Fourth of July heat.
According to multiple state environmental agencies and the U.S. Environmental Protection Agency (EPA), warm temperatures and nutrient-rich runoff are triggering widespread HAB activity—slimy, greenish mats of algae that can release toxins harmful to both people and pets.
Water that smells foul, appears foamy, or has paint-like streaks on the surface should be avoided, especially in popular swimming and boating areas. Exposure to HAB toxins can cause skin irritation, respiratory issues, nausea, and in severe cases, liver damage or neurological effects. Pets are especially vulnerable and should be kept away from shorelines with visible algae.
Arizona, Ohio, Florida, and several northeastern states have issued local warnings, with conditions expected to worsen through Sunday. In Arizona, the Department of Environmental Quality urges visitors to report suspicious water using azdeq.gov/AZHAB. In the Great Lakes region, NOAA satellite monitoring also shows blooms forming near shorelines and bays.
Health officials nationwide recommend:
- Avoid contact with water that looks or smells unusual
- Don’t allow pets to swim or drink from affected areas
- Wash thoroughly after being in natural waters
Stay alert for advisories, as algal bloom conditions can change rapidly with wind and water flow.
