Extreme heat has many flocking to the region’s lakes but some swimmers may want to think twice about jumping into the water.

Conservation authorities have issued advisories for four Guelph area beaches.

Guelph Lake, Belwood Lake, Rockwood and the Elora Quarry were tested earlier this week for E. coli bacteria.

The chance of illness is low but swimmers are told that they are entering the water at their own risk.

Dave Schultz with the Grand River Conservation Authority says the findings are not unusual based on the weather we’ve had so far this summer.

"E. coli is something that's found int he waste material from all living things, bird dropping, dog droppings. Over time, it just washes in to the lake and when you have warm weather like this it's a good environment for these things to multiply."

All four lakes have been tested again and the advisories could be lifted by Friday.