Hurricane Melissa strengthened into a Category 4 storm on Sunday, unleashing torrential rain and threatening to bring catastrophic flooding to the northern Caribbean.

The storm hit 75 mph winds to attain hurricane status on Saturday afternoon, the National Hurricane Center said. A tropical storm becomes a hurricane when its winds reach 74 mph. Melissa is set to become a major hurricane before the end of the weekend.

Melissa may be struggling now, but it is expected to rapidly intensify. It's also going to be a slow mover into early next week. Here's what that means for its forecast.

Hurricane Melissa threatens to make a direct strike on Jamaica as the most powerful storm in its history. See how strong it will become and where it’s headed.