The National Weather Service has issued multiple alerts for parts of central Maryland.

A flash flood emergency is in effect Saturday night for Howard County and southwestern Baltimore County, where officials said flash flooding was occurring and multiple water rescues had to be performed. Related: Water Rescues Underway in Ellicott City, Drivers Advised to Stay Inside

A flash flood warning is in effect until 4:15 a.m. on Sunday for parts of central Maryland. Flash flooding is already occurring in the region. Approximately 4 to 5 inches of rain have fallen in a short period of time, the National Weather Service reported before 9 p.m.

The following areas are included in the warning: Anne Arundel, Baltimore (city and county), Carroll, Frederick, Howard and Montgomery. Weather officials advise drivers to turn around—don't drown—if they see a water-covered road, as most flood-related deaths occur in vehicles.

Multiple swift water rescues have been reported in Ellicott City, where citizens are advised not to drive.

Locations where flooding is happening or anticipated are Baltimore, Columbia, Germantown, Rockville, Gaithersburg, Olney, Pikesville, Cockeysville, Elkridge, Damascus, Glen Burnie, Ellicott City, Dundalk, Towson, Catonsville, Woodlawn, Randallstown, Montgomery Village, Parkville and Owings Mills, according to the National Weather Service. A severe thunderstorm warning is in effect until 9:45 p.m. for Anne Arundel and Baltimore counties as well as Baltimore City.