The ice caves along Wisconsin's Apostle Islands National Lakeshore will open to the public on Saturday assuming conditions don't change, the National Park Service said Wednesday afternoon.

But they also urged caution for people who make the trek on Lake Superior ice.

"Rangers checked the ice today and found the walk to the ice caves very treacherous. Large areas of bare ice create extremely slippery conditions. Near the caves, piles of fractured ice sheets make footing rough and unsteady," the Park Service said in a Facebook post.

Rangers also said people should avoid recently formed cracks in the ice near the base of the cliffs and do not stand under large icicles.

The National Park Service's Julie Van Stappen warns the ice is very slippery.

"Unlike last year, when it was more like walking on a hard packed road, it's almost glare ice for a good chunk of the way," Stappen said. "So people really need to use some sort of crampons, and recommend that they bring ski poles, because it's just very slick."

The ice caves drew more than 138,000 tourists last year as the deep freeze made the caves accessible to pedestrians for the first time in nearly five years. In 2009, 12,700 visitors trekked to view the ice formations.

The crush of visitors in 2014 led the park system to plan a $5 fee this year for visitors age 16 and older.

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Apostle Islands ice caves to open Saturday