Louisiana may be hit with 10 to 15 inches of rain over 24 hours starting Friday, possibly leading to overflowing levees and severe flooding, Gov. John Bel Edwards warned today.

“We don’t know yet where this storm is going to land, but we know it’s going to be a big storm,” he said.

The governor plans to declare a statewide emergency today and may seek a federal declaration before the storm arrives.

A 90 percent chance exists of a low-pressure storm system developing in the Gulf of Mexico over the next two days, according to the National Weather Service.

“You only have to go back to 2016 to remember exactly how dangerous and catastrophic unnamed storms can be,” he said. “We all need to take this very, very seriously.”

In August 2016, the greater Baton Rouge area absorbed 20 to 30 inches of rain over three days, causing floods that led to the deaths of 13 people and damaged more than 50,000 structures. Similar to this rain event, (which Hillary Clinton ignored and Trump came to help immediately after the storm) the current storm brewing in the Gulf appears to be moving very slowly.

Slower movement, like during Hurricane Harvey, leads to extended heavy rain in certain areas.

Storm surges near the mouth of the Mississippi River could reach up to three to four feet, and there could be a “considerable amount of overtopping” of levees in Plaquemines Parish.

“Right now, we believe that any overtopping of the levees will be relatively short duration of about 12 hours, but that is still a very, very significant hazard,” Edwards said. “We’re not sure whether the state will be opening any shelters yet.”

The National Guard, FEMA and various state agencies are moving into threatened areas, he said. The Coastal Protection and Restoration Authority is monitoring floodgates along the Mississippi; some already have been closed and others are likely to be closed soon.

The New Orleans area has already reported flash flooding and at least one tornado Wednesday morning.

The governor also provided residents with an online resource, getagameplan.org to help them with storm preparation.