Workers secure plywood to business exteriors ahead of Hurricane Florence in Wilmington, North Carolina on Sept. 11. Photographer: Charles Mostoller/Bloomberg (Bloomberg)

Days before Hurricane Florence is expected to slam into the U.S. East Coast, insurers are starting to see potential claims costs tick upward as people flee and companies halt operations.

Evacuations, already affecting more than 1 million people in and around North Carolina, start the clock ticking on business-interruption insurance policies, which help replace lost income for companies when natural disasters strike. Hartford Financial Services Group Inc. and FM Global are among insurers with exposure in the region that are sending staff to help with anticipated claims.

“You’d have to expect, just based on the forecast, that it’s going to be a significant impact to businesses,” including prolonged disruptions, said Rick Miller, head of the U.S. property practice at Aon Plc. “Certainly businesses that take a direct hit, their facilities could be impacted for months.”

Making matters worse for insurers, forecasters say that Florence may stall over land, potentially dumping rain for days and causing power failures. The storm, expected to make landfall late Thursday or early Friday, may trigger “catastrophic flash flooding,” the National Weather Service said. Companies from agricultural firm Cargill Inc. to carmaker Daimler AG suspended operations in Florence’s path.

Florence could become the most powerful storm to hit the area in more than 60 years if its intensity continues. One estimate pegged the potential total costs of the storm at $30 billion.

Related: Boeing’s 787s flee Florence in a cross-country exodus

Banks are also limiting operations. PNC Financial Services Group Inc. had closed 24 branches in the Carolinas and coastal Virginia as of Tuesday afternoon, according to spokeswoman Marcey Zwiebel. Wells Fargo & Co. closed 20 North Carolina and Virginia branches and announced plans for 46 other early closures in the Carolinas, spokeswoman Ann Wasik said.

While the early evacuations could boost business-interruption claims, they can also allow firms the leeway to button up properties ahead of the storm.

“The better prepared anybody is, it can potentially reduce the impact of the claims if you can better harden your facilities against damage,” said Robert O’Brien, a managing director in the national property-claims practice at Marsh, a unit of Marsh & McLennan Cos.

Commercial insurer FM Global said it has a team in Atlanta, including more than 30 claims adjusters who are helping companies prepare for the storm and are ready to deploy into the area after Florence hits.

To see a map of storms in the region, click here

The effects of storms can ripple throughout the economy, especially if some companies hit by the hurricane are crucial suppliers to other firms, said Gary Love, vice president of operations underwriting at FM Global.

“It’s easy to think about the roof blowing off, the windows being shattered, but there’s more subtle parts of business interruption,” Love said. “You may not be physically damaged but you now don’t have electricity, or you don’t have water or you don’t have gas, so you can’t operate.”

Bryan Wood, a meteorologist and storm-damage analyst for Assurant Inc., said that Florence will hamper businesses even after it degrades from hurricane status.

“You look at power outages after hurricanes, they can last for a week more,” Wood said. “The winds themselves will decay pretty quickly, it’s just that persisting rain that’s going to be pretty dangerous.”

John Kinney, chief claims officer at Hartford, said three-quarters of the small businesses hit by Superstorm Sandy in 2012 had to close their doors for at least a day, with the average duration being about seven days. Only 11 percent of those businesses endured structural damage.

To contact the reporters on this story: Ivan Levingston in New York at ilevingston@bloomberg.net;Katherine Chiglinsky in New York at kchiglinsky@bloomberg.net

To contact the editors responsible for this story: Alan Goldstein at agoldstein5@bloomberg.net, Dan Reichl, Josh Friedman

©2018 Bloomberg L.P.