DENVER -- New testing by the Denver Department of Public Health and Environment shows higher than normal levels of bacteria in the water, including E. coli.
The recent hot temperatures encourage the growth of bacteria.
The 2018 Water Quality Report says most of the streams in Denver are not suitable for swimming at this time.
Jon Novick of the DDPHE said the South Platte River is a good example of how high temperatures affect the growth of bacteria in water.
"This river receives runoff from roads and streets it gets discharges from waste water treatment plants. You could be at risk of making yourself sick,” he said.
Health experts say people can become sick from E. coli bacteria by swallowing a small amount of water or wading with an open cut or sore.
The signs of illness include vomiting, diarrhea and fever.
The water should be safer once temperatures become cooler, but public health officials say regardless of the time of year, it's important to wash your hands before eating if you've been in any stream or lake.
The health department has an online map that shows updated water conditions.