The Sandusky River is expected to rise to 1.4 feet above flood stage by this afternoon, according to the National Weather Service.
At 2:45 p.m. Thursday, the river was at 7.5 feet with flood stage at 9 feet, according to the weather service.
Another storm system was expected to hit Northwest Ohio overnight Thursday.
The storm was expected to deliver an additional quarter-inch to half-inch of rain overnight, according to the National Weather Service.
The chance of precipitation was 100 percent.
Seneca County Emergency Management Agency Director Dan Stahl said the storm system, which was forecast to spread from the Gulf of Mexico into Northwest Ohio, was expected to leave behind an average of an inch of rain.
Stahl said with the ground already completely saturated from Wednesday's storm, flooding could be a major concern.
Surface water, water over roadways and the river system are a concern if significant rain fall hits the area, Stahl said.
He said drivers should be extra cautious on the roadways and always follow the slogan "Turn around, don't drown."
As of Thursday night, no roads in Seneca County were closed because of flooding.