(CNN) — Hurricane Matthew is pummeling the Bahamas. And its next stop could be the United States.
Here’s what you need to know now about the powerful storm that forecasters say is gaining strength:
• Authorities urged more than 2 million people to leave their homes in coastal Florida, Georgia and South Carolina as the storm neared — the largest mandatory evacuations in the United States since Hurricane Sandy hit the East Coast in 2012.
• Based on the latest projections, Matthew could make landfall in Florida early Friday as a Category 4 hurricane. It could also skirt the coast as it continues north.
• The storm has already killed at least 15 people in several Caribbean countries.
• It’s moving northwest at about 12 mph and packing 125 mph (205 kph) winds. Early Thursday it was about 60 miles (95 kilometers) southeast of Nassau, Bahamas, and 255 miles (410 kilometers) from West Palm Beach, Florida.
• If it strikes Florida, President Barack Obama warned, it could have a “devastating effect.”
Florida braces for direct hit
Florida Gov. Rick Scott warned 1.5 million residents they had 24 hours to get ready, or better yet, get going.
Scott has repeatedly warned that a direct hit by Matthew could lead to “massive destruction” on a level unseen since Hurricane Andrew devastated the Miami area in 1992. He has activated 1,500 National Guard members in preparation for the storm.
The voluntary and mandatory evacuations currently stretch from the Miami area all the way north to the Florida-Georgia border.
St. Johns County officials ordered 14,000 residents in St. Augustine, the oldest city in the US, to evacuate ahead of Hurricane Matthew starting at 6 a.m. ET Thursday.
Many residents found long gas lines Wednesday. However, Scott said the state is not experiencing any gas supply or distribution shortages. He also warned of the potential for prolonged power outages.
Airline passengers were urged to call before leaving for the airport. Fort Lauderdale’s airport is to close Thursday at 10:30 a.m. and FlightAware.com says almost 250 flights are canceled at Miami International Airport.
Scott said state offices will be closed Thursday and Friday in 26 counties. Six hospitals had started to evacuate patients, he added.
Palm Beach residents cleared many grocery store shelves ahead of the storm.
In Jupiter, resident Randy Jordan told CNN affiliate WPEC people were pushing and shoving their way through the local Home Depot to buy supplies ranging from batteries to flashlights.
Residents still had a sense of humor. Olivia A. Cole posted a photo on Twitter of an empty grocery shelf, save for eight cans of a soup typically enjoyed in another part of the country. “South Florida wants to survive #HurricaneMatthew. But we’d rather die than eat clam chowder,” Cole joked.
Mandatory evacuations in South Carolina
South Carolina Gov. Nikki Haley gave evacuation orders for the coastal counties of Charleston and Beaufort.
An estimated 250,000 residents evacuated from Charleston and Beaufort, said Kim Stenson, the director of South Carolina Emergency Management. He said as many as 200,000 people will leave Thursday.
Tempers apparently flared during the slow traffic out of Charleston. A man got out of his truck at a point where vehicles were being redirected, removed a traffic cone and sped away. Police chased the man until he stopped on a dead-end road. Berkeley County Chief Deputy Mike Cochran told CNN that the man fired at deputies and police officers, who shot back and wounded the man.
The man was hospitalized, but his condition is unknown.
The South Carolina Department of Transportation changed the directions of eastbound traffic lanes to accommodate the exodus of people leaving coastal cities like Charleston.
But as thousands fled inland Wednesday, not everyone chose to evacuate. In Charleston, which likely will see the powerful storm’s impact this weekend, some people were boarding up businesses.
“I think we’re staying put,” Cheryl Quinn told CNN’s Stephanie Elam.
Quinn and her husband said they were fine a year ago when Charleston endured heavy rain after a brush with a big storm.
“It was kind of a party down here. I hate to say that,” because storms can be scary, she added.
Still, Quinn has reserved a hotel room just in case.
North Carolina playing it by ear
North Carolina Gov. Pat McCrory declared a state of emergency for more than half the state’s 100 counties. So far, though, the governor has not urged residents to evacuate.
The changing forecast now predicts the storm won’t have as great an impact on the state as once feared, and Matthew might even turn around before it gets there.
“We’re just going to have to play it by ear and have our resources ready,” the governor said.
Officials are still concerned areas in eastern North Carolina that were recently flooded will see drenching rains from Matthew.
Georgia governor: ‘Remain calm, be prepared’
Georgia Gov. Nathan Deal has declared a state of emergency in 30 counties on or near the Atlantic Coast, and officials ordered a mandatory evacuation for Tybee Island, a low-lying island east of Savannah.
In six of those coastal counties — Chatham, Bryan, Liberty, McIntosh, Glynn and Camden — Deal urged more than 500,000 residents to voluntarily evacuate.
“Remain calm, be prepared and make informed, responsible decisions,” Deal said.