They said the department had responded to call after call, being drawn farther and farther into the county.
"Crews are responding to numerous swiftwater rescue calls involving cars that have become trapped in standing water," Armacost said.
While no injuries were reported, Armacost urged citizens to avoid unnecessary driving.
"If you must drive, do not attempt to drive through standing water," the release said. "It takes as little as 6 inches of moving water to carry away a vehicle."
With the school day coming to a close, Baltimore County Public Schools spokesman Charles Herndon said the school system was "keeping a close eye" on the ongoing heavy rains.
"I know there are a couple areas that we've had reports of standing water, but at this point, it doesn't appear to be disrupting [bus service]," Herndon said.
As of Thursday morning, Baltimore County officials updated the list of road closures — some due to flooding, others due to downed trees or even, in some cases, to roads and bridges that have been washed out.
Catonsville and Arbutus area:
• Hammonds Ferry Road and I-895
• Annapolis Road and the Anne Arundel County line
• Tulip Avenue and Daisy Avenue
• Tulip Avenue and Myrtle Avenue
• Unit block of Dogwood Drive
• Marriottsville Road between Wards Chapel and Powells roads
• Marriottsville Road at Granite Road
• 3300 block of Granite Road
• Windsor Mill and Mayfield roads