A severe thunderstorm warning is in effect for Harford and Baltimore counties until 6:15 p.m. on Thursday. Cecil County is under a severe thunderstorm warning until 6:45 p.m.
Winds greater than 70 mph and hail the size of quarters are possible, according to the National Weather Service. The storm was spotted in a line from Delta to White Marsh after 5:40 p.m. and was headed northeast, officials said.
The weather service advised staying indoors and away from windows.
The Maryland Transportation Authority said if drivers can't see the road, they should pull over and turn on their hazards until the storm passes.