Hurricane Matthew steamed toward heavily populated Florida with terrifying winds of 140 mph Thursday, and 2 million people across the Southeast were warned to flee inland, leaving more than 100 dead in its wake across the Caribbean. It was the most powerful storm to threaten the U.S. Atlantic coast in more than a decade, AP reported. "The storm has already killed people. We should expect the same impact in Florida," Gov. Rick Scott said as the skies began darkening from Matthew's outer bands of rain. The hurricane gained fury as it closed in, growing from a possibly devastating Category 3 storm to a potentially catastrophic Category 4 by late morning. It was expected to scrape nearly the entire length of Florida's Atlantic coast beginning Thursday evening. From there, forecasters said, it was expected to push along the coast of Georgia and South Carolina before veering out to sea. Millions of people in Florida, Georgia and South Carolina were told to head for safety, and interstate highways were turned into one-way routes to speed the exodus. Scott said Florida could be looking at its biggest evacuation ever. Many boarded up their homes and businesses and left them to the mercy of the storm.