As Arthur moves up the East Coast this week, lifeguards and weather experts warn visitors to be aware of rip currents and dangerous surf.

Rip currents are narrow, powerful channels of water that move away from the shore, Brad Reinhart, a meteorologist with the National Weather Service in Wilmington, N.C., told USA TODAY Network. They occur when there are a lot of waves crashing directly on the shore, he said.

There will be a high risk of rip currents in Wilmington on Thursday when the storm is closest to the beaches, Reinhart said, and an increased risk for several days after it passes.

"Basically, you get a lot of wave energy that piles up water along the shoreline, and that water has to go somewhere," he said. The water that has "piled up" then rushes back out into the ocean through breaks in between sandbars, creating rip currents. People who are caught in them are pulled away from the shore along with the water.