Heavy rain overnight caused the Allegheny County's sewer system to overflow into rivers and streams, leading the county Health Department to warn residents to avoid contact with stream and river water.

The warning, which is not for any specific location, was issued by the Allegheny County Sanitary Authority shortly after 5 a.m. Tuesday.

Health Department officials said those with weak immune systems and open cuts or sores should avoid contact with potentially contaminated water.

Guillermo Cole, a Health Department spokesman, said the warning is strictly advisory based on the fact that significant rainwater can cause sewers with both sewage and rainfall running through them to overflow.

Tuesday's warning is the second since the boating season began May 15.

Channel 11’s news exchange partners at TribLIVE contributed to this report.