CLEVELAND, Ohio -- Beachgoers aren't allowed to swim at Edgewater Beach after heavy rain on Monday night caused stormwater and raw sewage to drain into Lake Erie.

About 130,000 gallons flowed into the lake. The Northeast Ohio Sewer District issued a swimming advisory Tuesday morning and is testing the water in the morning and afternoon to check bacteria levels.

It will take 24 hours to process these samples, district spokeswoman Jennifer Elting said.

Cleveland Metroparks lifeguards will be on duty from 11 a.m. to 7 p.m. Tuesday to let guests know the swim area is closed. Visitors will be permitted on the sand and at the beach house, spokeswoman Jacqueline Gerling wrote in an email.

An example of the swimming advisory signs posted Tuesday at Edgewater Beach (Northeast Ohio Regional Sewer District)

The runoff was caused by a "combined sewer overflow" which happens when too much wastewater enters the system for sewers to handle, according to the district. The overflow happened just before midnight.

About an inch and a half of rain fell between 10:15 p.m. and 10:45 p.m., Elting said.

The last time the district posted a swimming advisory because of the combined sewer overflow was in June of 2015. There was also an overflow in November of 2017, but it was outside of swimming season.

This used to happen more frequently though. The overflow system that directs combined sewage to Lake Erie is about 100 years old and remains from before treatment plants were built to deal with sewage. Back in the 1970's, the combined sewer overflow would go off 40 to 50 times a year, Elting said.

The wave of strong thunderstorms also knocked out power for thousands of people. FirstEnergy estimated nearly 4,000 people were left without power just before 5 a.m. on Tuesday, according to cleveland.com's Cliff Pinckard.

The storms could continue. According to cleveland.com's Kelly Reardon, scattered storms are possible across Northeast Ohio for Tuesday. You can find weather forecasts here.

Beachgoers will see signs indicating the swimming advisory. Check the sewer district's website for more updates, or follow @neorsd or @neorsdbeaches on Twitter. The Metroparks will also post updates.