Hurricane Matthew is a serious threat to Florida, Georgia, South Carolina. Here's what we know.

Hurricane Matthew is no joke. The major Category 3 storm is poised to inflict serious damage as it buzzes along the coasts of Florida, Georgia, and South Carolina from Friday through Sunday:

If you have been told by local officials to evacuate and that there is still time to leave, go now! Your life could depend on it! #Matthew

— Dr. Rick Knabb (@NHCDirector) October 7, 2016

The storm has already left 300,000 people in Florida without power. Authorities have told more than 2 million residents in these three states to leave their homes and take shelter. Officials even reversed lanes on I-26 so that cars can drive out of Charleston faster.

Here’s the latest forecast of the storm's path from the National Hurricane Center, as of 5 a.m. on Friday. There are hurricane warnings for the entire area marked in red:

(National Hurricane Center)

Matthew has already rampaged through Haiti, leaving more than 478 dead. Now it’s running roughly parallel to the US coast, pummeling the Southeast with destructive winds and storm surges.

Although Matthew is no longer expected to make landfall in Florida or Georgia, sparing the region the very worst impacts, it is still a tremendous threat. The storm has maximum sustained winds of 110 mph, with hurricane-force winds (at least 75 mph) extending 60 miles out from its center.

NEW track from NHC has #Matthew NOT making landfall. Great news, but 100+mph winds, rain & storm surge still likely pic.twitter.com/kXocXDbRnH

— Micahharriswx (@micahharriswx) October 7, 2016

The National Weather Service is warning people along the coast of Florida, Georgia, and South Carolina to prepare for "life-threatening situations," such as:

• Massive storm surges. Some regions could see severe flooding as high as 7 to 11 feet. Downtown Jacksonville is expecting 3 feet of flooding. South Carolina could see flash floods.
• Hurricane-force winds could do structural damage to buildings and homes. Some roads and bridges could be impassable from fallen trees and other large debris.
• Widespread power and communications outages.

The Kennedy Space Center in Cape Canaveral , one of NASA’s key launching pads, is also bracing for high winds and could suffer damage.

The roof just ripped off the house we are next to. That was one strong wind gust. Cape Canaveral, FL @TheWeatherNetUS @StormhunterTWN pic.twitter.com/HIPUiF6ceP

— Jaclyn Whittal (@jwhittalTWN) October 7, 2016

That said, this storm could have all been much, much worse. If Matthew had veered just a little bit to the west, it would have made landfall as a Category 4 hurricane, the first major hurricane to do so in the United States since Hurricane Wilma 11 years ago. That would have brought winds strong enough to destroy mobile homes, uproot large trees, and rip the roofs right off buildings.

The storm's exact track going forward is still uncertain, so watch the forecasts. The National Hurricane Center is a reliable source of information and issues updates regularly.

Hurricane Matthew has already devastated Haiti — killing more than 478

(NASA Goddard Flight Center)

Many Americans are just tuning in to Matthew, but this storm has been wreaking havoc in the Caribbean all week.

The storm made landfall in Haiti on Tuesday, October 4, as a Category 4 storm, the strongest to hit the nation in more than 50 years. The country received several months’ worth of rainfall in a single day, causing horrific flooding:

(HECTOR RETAMAL/AFP/Getty Images)

The storm hit the country’s southwestern region particularly hard, and the damage has been catastrophic in those areas. At least 478 people are dead, and in some towns hundreds of homes have been flattened. Relief workers are still struggling to reach the affected areas, and this could end up being the country's biggest disaster in years:

AP Photo/Dieu Nalio Chery

The storm also slammed into Cuba on the same day, forcing 700 Americans to evacuate the military base in Guantanamo Bay.

Fortunately for Cuba, Matthew mostly rolled through sparsely populated areas in the east of the country. But those in the city of Baracoa were battered with 145 mph winds and torrential rains, and plenty of homes were destroyed:

AP Photo/Ramon Espinosa

On Thursday, Matthew moved north through the Bahamas, downing trees and power lines in Nassau:

No deaths have yet been reported here, but the country is still assessing the damage. While the storm weakened after running over these islands, it then picked up strength in the unusually warm Gulf Stream current before veering toward Florida.

Hurricane Matthew is unusual in a couple of respects

Matthew first formed back on September 29. And while it’s not the strongest storm ever seen, it has reached some impressive milestones, as Colorado State meteorologist Phil Klotzbach explains over at Capital Weather Gang:

• Matthew remained a Category 4 or 5 storm for 102 hours, longer than any other hurricane in the eastern Caribbean.
• At one point, Matthew intensified from a Category 1 to a Category 5 storm in just 24 hours, which only two other hurricanes have done (Hurricane Wilma in 2005 and Hurricane Felix in 2007).
• The storm has remained at least a Category 3 hurricane for more than five days, the longest-lived major hurricane since Hurricane Ivan in 2004.

Whenever unusual hurricanes hit, people sometimes wonder about the climate change context. Chris Mooney at the Washington Post has a good breakdown here. Many meteorologists will point out that it’s tough to disentangle all the different factors involved (there were certainly Category 4 hurricanes before we ever started burning fossil fuels). But we do know that the oceans are unusually warm right now, which can fuel strong hurricanes, and sea levels are higher than in the past — which certainly exacerbates storm surges and flooding.

Another reason Hurricane Matthew could prove more costly than previous storms is the simple fact that there are 2 million more people living on Florida’s coasts than there were in 2005. More people and homes means more stuff for a large storm to damage. This image from Stephen Strader of Villanova University makes the point well:

Housing exposure change 1940-2010 pic.twitter.com/1t3pTMLMxs

— Stephen M. Strader (@StephenMStrader) October 6, 2016

Further reading

— The National Hurricane Center is offering frequent updates on Matthew. If you live anywhere near the path of this storm, you should be checking this out. Also follow them on Twitter.

— Also bookmark the Capital Weather Gang and Jeff Masters at Weather Underground, both of which offer frequent and detailed updates.

— A look at how officials try to persuade stubborn residents to evacuate dangerous areas. One trick? Tell them if they want to stay, they should write their Social Security numbers on their arms in permanent marker, so that police can identify their corpses. Makes the threat vivid.

— A very basic guide to how hurricanes form

Watch: Remembering Katrina and the aftermath

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