It's too soon to know exactly where Hurricane Matthew will be in a few days, or how hard it will hit the United States but Florida Gov. Rick Scott says evacuation orders could come as early as Tuesday as Hurricane Matthew approaches. South Carolina Gov. Nikki Haley says coastal evacuations will begin Wednesday.
"We have to be prepared for a major hurricane," Scott said. "We have to prepare for a direct hit."
The governor told residents along the state's east coast: "If you are able to leave early, leave now."
He said he plans to activate 500 additional National Guard members by Wednesday morning.
The storm's latest track shows it making a westward turn toward the US East Coast. Officials in several states in that region say they're not taking any chances.
"We cannot take it lightly. It is absolutely deadly. It's approaching Florida with potentially devastating winds," Scott said at a news conference earlier Tuesday morning. "Every forecast continues to put Florida more in harm's way. If Matthew directly impacts Florida, there will be massive destruction that we haven't seen in years."
CNN forecasters predict the storm could hit parts of Florida starting Thursday night.
The National Hurricane Center issued advisories for parts of the Florida coast. A hurricane watch extends from Deerfield Beach to the Volusia/Brevard county line, including Boca Raton, West Palm Beach, Fort Pierce, Vero Beach and Cape Canaveral.
A tropical storm watch has been issued from the central Florida Keys northward to Deerfield Beach, including Marathon Key, Miami and the Fort Lauderdale metropolitan area.
Officials may issue evacuation orders later Tuesday, the governor said.
"If an evacuation order is issued in your area, leave immediately. ... Once the storm comes, we cannot put our first responders in harm's way," Scott said. "You must leave before it's too late. You can rebuild a home. You can rebuild a business. You cannot rebuild a life."
Scott declared a state of emergency for his entire state. North Carolina Gov. Pat McCrory has declared a state of emergency for more than half of the counties in his state.
South Carolina Gov. Nikki Haley said the state would begin medical evacuations ahead of Hurricane Matthew at 3 p.m. Tuesday and will begin coastal evacuations on Wednesday. She said residents should travel 100 miles away from the coast.
About one-million people are expected to move inland, including Fred and Paula Duda who live in Sun City Hilton Head in Bluffton, SC.
"When I got home from work [Tuesday], all of the neighbors were out helping each other put the storm shutters up," said Fred Duda.
"Stores are jammed. ATMS have 4 to 5 people in line waiting. As I was coming into work in Savannah, there was almost a solid line of traffic heading out of Hilton Head," he said.
Paula Duda added, "At the gas stations, there's a 2 hour wait for gas. I couldn't get out of work because of the gas line."
Georgia Gov. Nathan Deal issued a state of emergency in 13 coastal counties ahead of the storm.
The potential threat was enough for Rick Knabb, director of the National Hurricane Center, to fire off a warning to Americans.
"U.S. East Coast: find out today if you live in an evacuation zone," Knabb tweeted. "If so, decide where you'd go, how you'd get there if told to go."
Florida residents will likely see tropical storm and hurricane watches later Tuesday morning, forecasters said.
The "extremely dangerous" Category 4 hurricane made landfall in western Haiti Tuesday morning and was heading toward Cuba with winds of 145 mph, according to the hurricane center.