The US Coast Guard ordered ship operations to cease at the country’s fourth-busiest container port as Hurricane Idalia became stronger than expected overnight.

The agency’s Homeport site said the port of Savannah was in Condition Zulu as of Tuesday night, meaning ship operations are suspended.

The Zulu status also applies to the port of Brunswick, also in the East Coast state of Georgia.

The closures came as Idalia strengthened to unexpected ferocity, briefly becoming a Category 4 storm before making landfall in the Big Bend region of Florida.

TradeWinds reported on Tuesday that ports across the state’s Gulf Coast were in condition Zulu, including the cargo and passenger ports of the Tampa area.

It is not clear how those ports have fared in the storm. While the brunt of Idalia’s ferocity appears to have been unleashed further north, local news in Tampa reported on flooding and wind damage in the area.

Hurricane Idalia slammed into the Florida coast on Wednesday morning, after weakening to a Category 3 storm. It is currently a Category 2 storm, with its currently projected path threatening a direct hit on the city of Savannah later in the afternoon.

The National Weather Service issued a hurricane warning for Savannah early Wednesday, forecasting that the storm will have Category 1 strength upon its arrival. The agency warned that preparations should be made for a Category 2 storm.

Savannah is the major container gateway for the southeastern US, including the largest single-box terminal in the country. The port also handles ro-ro, breakbulk and project cargoes.

Further south, Brunswick is a major ro-ro port, handling 900,000 vehicles per year.