Miami-Dade County ordered some mandatory evacuations, including for Key Biscayne and Miami Beach, as well as for areas in the southern half of the county that are not protected by barrier islands.
“EVACUATE Miami Beach!” Miami Beach Mayor Philip Levine tweeted, later noting in a news release that once winds top 40 mph, first responders will no longer be dispatched on rescue missions here.

Other evacuation zones were in place across much of South Florida. States of emergency also were declared in Georgia, South Carolina and North Carolina in anticipation of Irma’s path early next week.

Scott, the Florida governor, ordered that all state offices, public schools, state colleges and state universities be shut down from Friday through Monday “to ensure we have every space available for sheltering and staging.”

Still, it was unclear where Irma will make landfall.

“The wild card here is the turn. Anytime a hurricane makes a turn, it introduces uncertainty,” Mark DeMaria, acting deputy director of the National Hurricane Center in Miami, told The Washington Post in the center’s headquarters in west Miami-Dade County.

DeMaria noted that the computer models have fluctuated modestly, with adjustments in the consensus track of 50 miles or so every day. “But 50 miles onshore versus right of the coast makes a huge difference in impact,” he said.

The combination of Florida’s geography, the pattern of urban settlement in narrow bands along the coasts and the projected northerly path of the hurricane presents a particularly ominous picture.

“This is a large storm coming from the south,” said Dennis Feltgen, spokesman for the hurricane center. “That’s the worst-case scenario, because it takes in the entire Gold Coast population, and you have the greatest impact from storm surge from that direction.”

At the National Hotel on Miami Beach, a manager announced Thursday in four languages — English, Spanish, Portuguese and French — that guests needed to evacuate because of a city order. At the front desk, guests were given a sheet listing the locations of emergency shelters, none of which were likely to be as nice as the beachfront Art Deco hotel, which was restored a few years ago.