Hurricane Irma, a potent storm at the top of the classification scale with winds above 180 mph, was bearing down on the Caribbean on Tuesday, prompting national parks in its path to shutter their operations.

Virgin Islands National Park in the U.S. Virgin Islands closed the Cruz Bay Visitor Center Tuesday until further notice, and cancelled all park programs. Hurricane Hole, considered a safe harbor during storms, was open.

On the mainland, Biscayne National Park closed its visitor center, island visitor facilities, and administrative facilities on Tuesday to prepare for the storm, while officials at Everglades National Park were keeping an eye on the storm and had not yet shut down any visitor facilities.

At Biscayne, "boating in park waters remains open, including the Intracoastal Waterway and other channels. Visitors planning to boat in the park should monitor VHF radio for weather conditions and follow marine advisories," the park advised.

Dry Tortuga National Park was scheduled to close at 8 a.m. Wednesday, while Big Cypress National Preserve on the mainland was scheduled to close at noon Wednesday.

"Visitors planning to access the backcountry prior to the closure should stay advised of weather conditions and be prepared to leave if conditions worsen. Please allow extra time to depart from the backcountry and evacuate the area during inclement weather," a release from Big Cypress said.

According to the National Oceanic and Atmospheric Administration's Hurricane Center, Irma was on course to make landfall in Florida sometime this coming weekend. 

"Irma is an extremely dangerous category 5 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some fluctuations in intensity are likely during the next day or two, but Irma is forecast to remain a powerful category 4 or 5 hurricane during the next couple of days," the Hurricane Center forecast Tuesday evening. "Hurricane-force winds extend outward up to 60 miles from the center and tropical-storm-force winds extend outward up to 175 miles."

In a more detailed discussion of Irma, the forecasters said, "The chance of direct impacts from Irma beginning later this week and this weekend from wind, storm surge, and rainfall continues to increase in the Florida Keys and portions of the Florida Peninsula. However, it is too soon to specify the timing and magnitude of these impacts."