Tropical Storm Debby reached Florida’s gulf coast early Monday as a hurricane, bringing with it catastrophic flooding as it slowly passed over the northern part of the state. It was later downgraded to a tropical storm, but forecasters warned that record-setting rain could pummel coastal Georgia and South Carolina in the coming days as the system heads east.

The storm made landfall as a Category 1 hurricane near Steinhatchee, a tiny community in northern Florida of less than 1,000 residents. The storm came ashore in one of the least populated areas of Florida, but forecasters warned heavy rain could spawn dangerous flooding.

The hurricane caused flights to Florida, including Miami, and the south to be cancelled on Monday.

The small community where Hurricane Debby made landfall is roughly 32 km. from where Hurricane Idalia crashed ashore less than a year ago.

“That part of the coast is a very vulnerable spot,” said John Cangialosi, a hurricane specialist with the National Hurricane Center. Some areas has already received 25 to 30 cm. of rain.

More than 350,000 customers were without power in Florida and Georgia by midday Monday, according to PowerOutage.us and Georgia Electric Membership Corp.

Debby weakened into a tropical storm late Monday morning, with top winds hovering around 110 kph. The storm was moving slowly to the north-northeast, and was expected to decrease in speed as it turns to the east, forecasters said.

In Savannah, Georgia, local leaders said flooding could happen in areas that don’t usually get high water if Debby stalls out over the city.

In South Carolina, Charleston County Interim Emergency Director Ben Webster called Debby a “historic and potentially unprecedented event” three times in a 90-second briefing Monday morning.

The city of Charleston has an emergency plan in place that includes sandbags for residents, opening parking garages so residents can park their cars above floodwaters and an online mapping system that shows which roads are closed due to flooding.

North Carolina and South Carolina have dealt with three catastrophic floods from tropical systems in the past nine years, all causing more than $1 billion in damage.