Charleston City Council on Thursday unanimously passed a resolution declaring a state of emergency in the city, as Charleston, Berkeley and Dorchester counties have done.
Mayor John Tecklenburg said in a phone conference with Council that the resolution would ensure the city is eligible for Federal Emergency Management Agency reimbursement for any damage caused by Hurricane Irma.
Emergency Management Director Mark Wilbert said the city is preparing for Category 3 winds by late Sunday.
He said if Hurricane Irma remains on its projected track to make landfall in or near South Carolina late Monday or early Tuesday, the city's biggest concern will be storm surge.
"Storm surge and inundations is probably the thing we’re most at risk for, even probably more so than wind," he said, adding it's too soon to know how much water Irma could hurl onto the coast.
"We don't even have really good, accurate predictions yet, and we won't get those until a hurricane watch is posted for the area, when the National Hurricane Center will begin to run those models," Wilbert said.
He said all city departments will operate as usual through Friday afternoon.
"We made the decision because we have work to do to get the city ready," he said.
In a press conference held after the phone call with council, Wilbert said residents shouldn't compare Hurricane Irma with Hurricane Matthew, which hit the South Carolina coast in October.
"It is much more dangerous than Hurricane Matthew," he said. "Prepare now for an evacuation. Do not delay."
Residents will be able to store their cars in city parking garages for free starting at 5 p.m. Friday.
Tecklenburg said the city handed out nearly 20,000 sandbags, about 5,000 more than it did during past hurricane preparations.
City crews are now cleaning out storm water drains to ensure they can accept the most possible water during the storm. Also, the city has rented portable pumps to help push water out of seriously flooded areas, he said.
Greg Yee contributed to this report.