The expected upgrade back to Cat 4 is now official 10 Sept
- currently about 40miles (65km) south-southeast of key west Florida
- maximum sustained winds of 130mph (209km/h)
Hurricane force wind gusts are battering islands in Florida's south, the governor says, with the mainland due to be hit in the coming hours.
In Florida, 6.3 million people - about 30% of the state's population - have been told to evacuate. But yesterday the state governor said it was now too late to leave for anyone remaining.
The National Hurricane Center has issued warnings against "life-threatening" storm surges in the Florida Keys as well as Tampa Bay and other coastal areas. More than 200,000 homes in the state have been affected by power outages, with 164,000 outages in Miami Dade county alone.
The western Gulf coast is expected to be worst affected, with cities such as Tampa and St Petersburg in the path of the storm.The Tampa Bay area, with a population of about three million, has not been hit by a major hurricane since 1921.
The BBC has more here
Awful news unfolding. Let's hope for the minimum expected damage and loss of life
