For the latest on Hurricane Irma, read this article.

Hurricane Irma strengthened over the Atlantic Ocean into “an extremely dangerous” Category 5 storm on Tuesday, threatening to batter the Caribbean and, potentially, Florida, too, according to the National Weather Service.

Irma is expected to retain Category 4 or 5 status for days as it makes its way through the Caribbean, most likely hitting the islands of Antigua and Barbuda as soon as Tuesday night, according to a weather service meteorologist. Florida, where evacuations have already been announced, is increasingly likely to feel Irma’s effects later this week and over the weekend, though the storm’s potential severity is not yet clear.

“There are different scenarios and we really won’t know which one of those is going to be the case until a couple days beforehand,” said Chris Landsea, a meteorologist with the National Hurricane Center in Miami.

Still, the weather service urged people living in hurricane-prone areas to have plans in place should it hit. And officials in the Florida Keys announced that a mandatory evacuation would begin on Wednesday. The mayor of Miami-Dade County, which is home to 2.7 million people, warned residents that evacuations might be forthcoming as soon as Wednesday, too.