National Park System units along the Carolinas were making plans Tuesday to close before the remnants of Hurricane Idalia reached them.

While the hurricane was expected to be downgraded to a tropical storm by the time it reached those states, the impacts were still expected to be substantial.

"Storm impacts, including high winds up to 36 mph and between 4-6 inches of rain, will begin affecting our region starting on Wednesday and continue through the morning hours of August 31," noted Congaree National Park staff in South Carolina. "The most hazardous conditions are likely to occur in the overnight hours as the storm passes through our area. These conditions can result in numerous trees and large branches capable of heavy damage and/or severe injury, to fall."

As a result, the park planned to close to the public at noon Wednesday.

Cape Hatteras National Seashore staff in North Carolina said the Ocracoke, Cape Point, and Frisco campgrounds would close Wednesday and reopen after post-storm assessments are completed. "As more forecasts are issued by the National Weather Service, additional closures of visitor facilities may be necessary," the staff added.

"Due to swells produced by distant Hurricane Franklin and elevated tides, some seashore oceanside beaches are experiencing erosion and overwash," the advisory continued. "Portions of off-road vehicle routes on Hatteras and Ocracoke islands may be impassable until this weekend. Life-threatening rip currents are expected through the next several days. Seashore visitors should stay out of the ocean until conditions improve. A two-mile stretch of beach between the north end of Rodanthe and South Shore Drive in Rodanthe should be avoided due to the continued presence of vulnerable houses that may be damaged by rough surf and strong winds."

At Cape Lookout National Seashore just south of Cape Hatteras, staff said a combination of events — the two hurricanes, plus a "king tide," a particularly high tide due to a full moon — would make conditions dangerous at times for visitors. As a result, staff was "highly discouraging campers and other overnight visitors from staying in the park from this Wednesday through this Friday. All other visitors should be very aware of the pending conditions described below. There are plenty of great times to spend a few days at the Cape — this isn’t one of them."

• Tropical Storm/Hurricane Idalia, currently heading towards Florida as a Hurricane, is predicted to pass very close to Cape Lookout late Wednesday night/early Thursday morning as a Tropical Storm (winds in the 39 - 55 mph range). It is expected to drop a large amount of rainfall and produce strong winds in the area.
• Hurricane Franklin is still several hundred miles offshore. The storm is sending large swells our way and creating dangerous rip currents along the beaches as it continues its path northward in the Atlantic.
• "We are in a king tide event from August 27th until September 4th. This includes several very high tides (over 5 feet) over the course of the next few days," the seashore said.

"The combination of two major storms and a king tide at the same time will create hazardous conditions on the islands of Cape Lookout National Seashore. We currently expect that the islands will see substantial overwash and flooding. As Idalia passes over the islands, it is expected to drop between 6 and 8 inches of rain," Cape Lookout reported. "Franklin’s swells will continue to present extremely dangerous rip currents throughout the week. Both storms will push large amounts of water toward land, moving the flood-inducing impacts of king tides onto even higher ground."

On Monday, Dry Tortugas National Park and Timucuan Ecological and Historic Preserve in Florida and Fort Pulaski National Monument and Cumberland Island National Seashore in Georgia closed ahead of the storm, and Castillo de San Marcos and Fort Matanzas national monuments in Florida planned to close Tuesday.