Gov. Josh Stein of North Carolina declared a state of emergency on Tuesday as the outer bands of Hurricane Erin inched closer to the state, increasing the likelihood of life-threatening rip currents this week.

“To folks on the coast, now is the time to prepare,” Mr. Stein wrote on social media. “Check your emergency kits, make sure you have emergency alerts turned on, and listen to emergency guidance in case you need to evacuate.”

The state’s emergency management agency said that storm surge, or the abnormal rise of water generated by a storm, could reach as high as four feet on Wednesday. Portions of the Outer Banks in North Carolina are under a mandatory evacuation order, and officials have warned that some roads could remain impassable for days.

By Tuesday afternoon, many tourists had already hopped on a ferry and fled places like Ocracoke, a small coastal community that is reachable only by boat.

Farther south, on beaches near Wilmington, the sun was shining, and there were still plenty of people enjoying the last dribbles of good weather. People played music and read on the sand, even as lifeguards remained on high alert.

In Wrightsville Beach, about 70 people had to be rescued on Monday from dangerous rip currents generated by swells from Hurricane Erin. Officials have warned residents not to swim in the area until at least Friday.

“It’s like a perfect storm,” Sam Proffitt, the town’s ocean rescue director, said in an interview on Tuesday. “The weather is nice. It doesn’t look super choppy. People just see waves, but it generates a lot of rips.”

Aidan Kratt, 22, who works at Sweetwater Surf Shop near Wrightsville Beach, said that while he surfed on Monday for about 15 minutes, he saw lifeguards rescue at least three people who had been sucked far from shore by powerful currents.

As he rested on his board in the surf, Mr. Kratt said he saw a woman’s head bobbing above the water far from him, appearing to struggle.

“I could tell she was a little tired, and there was already a no-swim advisory red flag, so I just helped her back, just in case,” Mr. Kratt said. “You can just get pulled out in two minutes and not even really know it.”

She hung onto his board as he paddled them to shore.

Jerry Slayton, a manager at Cavalier Surf Shop in Nags Head, a beach town in the Outer Banks, said many locals didn’t appear too concerned about the storm quite yet, based on the forecast as of Tuesday.

“I just hope it doesn’t flood too much,” he said as he closed up shop, after a day of serving customers who were eager to buy the right gear for increasingly powerful waves.

“It’s pretty good out there, so the surfers are happy,” Mr. Slayton added. “The tourists are a little bummed.”

Michael Levenson contributed reporting.