CHICAGO (WLS) — There is a risk of flooding and sewer backups Friday morning across the Chicago area as heavy rain moves in.

Rain, drizzle and fog began to move into the area Thursday evening, ABC7 Meteorologist Larry Mowry said.

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A Dense Fog Advisory has been issued for almost every county in Illinois, including all counties in the Chicago area, until 9 a.m. Friday, the the National Weather Service said. On the very southernmost tip of the state is not under the advisory.

As of 7:45 p.m. Thursday, the National Weather Service has not yet issued any official flood watches for counties in the Chicago area.

The heaviest rain is expected between 6 a.m. and noon Friday. Because the ground is frozen, heavy downpours can run off and cause flash flooding as the rain won’t seep into the soil, Mowry said.

FULL FORECAST | Chicago weather: Mild with rain late Thursday

Officials are also keeping a close eye on Chicago-area rivers that may be at risk for flash flooding due to melting ice. There were near-record high temperatures Thursday across the area.

Water management officials said Friday will be an overflow action day.

The Metropolitan Water Reclamation District of Greater Chicago issued an alert Thursday asking people to delay showers and baths, flush less frequently and wait to run the dishwasher or washing machine. More information can be found here.

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