If Hurricane Irma makes landfall in the continental United States as a Category 5 hurricane, it will be only the fourth time such a powerful storm has smashed into the mainland since modern record-keeping began.

The unnamed 1935 Labor Day Hurricane, Camille of 1969 and Andrew of 1992 all struck Florida and the Gulf Coast as the highest level tropical systems.

Irma's fate is uncertain, said meteorologist Gavin Phillips, of the National Weather Service's Slidell office. Traveling overland weakens storms, so if the hurricane traverses several Caribbean islands, it may hit the lower 48 at a lower strength, he said.

The National Hurricane Center is projecting Irma to make landfall Sunday near Miami, though the forecast could change, and it may track farther north before striking land.

"Twenty miles could make a big difference," Phillips said.

The worst-case scenario, he said, would be if the storm hugs the coast, battering ocean-side cities without ever making the landfall that would sap its energy. In such a case, Irma could hammer communities from Miami to Savannah, Georgia to Charleston, South Carolina. Similar circumstances made Hurricane Matthew so destructive in the U.S. and the Caribbean last year.

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Hurricane Harvey caused much damage to Texas because of the amount of rain it dropped, causing widespread flooding. The major concerns with Irma, however, are from high winds and the storm surge — when tropical weather pushes sea water onto land — Phillips said.

Meanwhile, two other named systems have formed in the Atlantic and the Gulf of Mexico.

Hurricane Jose is still far to the east in the Atlantic. The most recent National Hurricane Center forecast has it swinging to the north in an arc that would miss Puerto Rico and the rest of the Caribbean.

Meanwhile, Hurricane Katia formed in the Gulf of Mexico and is expected to run aground near Veracruz, Mexico, in the coming days.

Follow Steve Hardy on Twitter, @SteveRHardy.