Gusts of wind have already exceeded 90 miles an hour off the coast of Louisiana.
Hurricane Sally is targeting the Gulf Coast, where dangerous storm surges and historic and life-threatening floods are expected this week.
Sally is expected to crawl very slowly across the northern Gulf of Mexico over the next 24 hours and land near the coast of Dauphin Island, Alabama on Wednesday morning.
Gusts of wind have already exceeded 90 miles per hour on oil platforms off the coast of Louisiana and Alabama.
The highest storm surge is likely to be in eastern Louisiana and near Mobile Bay, Alabama, where the tide could reach 4 to 7 feet.
Even in Florida and parts of Lake Pontchartrain, Louisiana, which is on the north side of New Orleans, storm surge of up to 4 feet is possible.
Total rainfall could reach 30 inches in Alabama and the Florida Panhandle.
Sally will then crawl inland across Alabama and Georgia.
Atlanta could see 6 to 12 inches of rain by the end of the week.
Florida Police began closing the Pensacola Bay Bridge, which connects Pensacola to Pensacola Beach, Tuesday.
“We urge you to stay at home and away from the streets when you can,” said Pensacola police.
Alabama Governor Kay Ivey ordered the beaches to close on Monday afternoon, saying she recommends “evacuation, especially of non-residents and those who live in flood-prone areas south of I-10.”
“Sally is becoming a very dangerous and historic flood event,” said Brian Hastings, director of the Alabama Emergency Management Agency, on Tuesday. “If you are in a lower or flood-prone area, move to a safer place.”
New Orleans Mayor LaToya Cantrell said residents outside the levee protection system would need to evacuate.
In Hancock County, Mississippi, officials ordered mandatory evacuation from low-lying areas.
In Biloxi, Mississippi, casino resorts have been ordered to close.
“We have two concerns,” said Biloxi Mayor Andrew Gilich on Monday. “First, that our residents are taking this seriously and have made preparations, and second, that this is a slow storm, which means that we will see severe flooding on the front beach and in lower-lying areas, especially along the rivers and bay. “
“Residents need to have a plan and follow that plan,” he said.
Sally is the seventh hurricane this season. The average is currently six.
Sally will be the third hurricane to land on the Gulf Coast this season.
The storm will also be the fourth hurricane to land in the United States this season. The last time the nation had more than four hurricanes to land was in 2005 when there were five, including Hurricane Katrina.
This report was published on Tuesday, September 15, 2020, on the episode of “Start Here,” ABC News’ daily news podcast.
“Start Here” offers a simple look at the top stories of the day in 20 minutes. Listen for free every weekday on Apple Podcasts, Google Podcasts, Spotify, the ABC News App or wherever you get your podcasts.