Florida is bracing for what could be the United States’ heaviest-hitting hurricane so far this season, as an area of thunderstorms builds strength in the Caribbean Sea before potentially bringing life-threatening storm surge and hurricane-force winds to the Southeast later this week.

Winds with a tropical disturbance in the Caribbean Sea are forecast to intensify to near-hurricane-force, National Hurricane Center says.

Hurricane John has been downgraded to a tropical storm and is moving northwestward, the U.S. National Hurricane Center said in its latest advisory. The storm was about 115 miles (185km) north west of Punta Maldonado Mexico,

John was a tropical storm over Mexico early Tuesday Mexico Central Time, the National Hurricane Center said in its latest advisory. The tropical storm had sustained wind speeds of 70 miles per hour. Flash flooding can occur well inland and away from the storm’s center.

Hurricane John is expected to bring dangerous winds, storm surge and life-threatening flash flooding to parts of southern Mexico.

Hurricane John struck Mexico’s southern Pacific coast with life-threatening flood potential after growing into a major hurricane in a matter of hours. It came ashore near the town of Punta Maldonado late Monday night as a Category 3 storm with maximum sustained winds of 120 mph (190 kph).