WEALTHWOOD, Minn. (WCCO) – Despite warnings about thin ice, 30 people had to be rescued off the North Shore of Lake Mille Lacs Wednesday night.

The Aitkin County Sheriff’s Office had to send out boats, rescue sleds and a hovercraft to rescue the fishermen from a floating ice sheet.

WCCO-TV saw plenty of people are still on the ice on Thursday, despite all the open water on the lake.

Frightening is how one fisherman describes the ice conditions on the popular lake. It’s not been the start to the season resorts and anglers were hoping for.

With no snow cover to insulate, conditions should be ideal for building a thick covering on Minnesota’s favorite winter fishing lake. But for anglers, warm and windy conditions make for an unpredictable freeze up.

“I went out about 300 yards and I found 8 to 10 inches of ice, then 50 yards away from me it was 2 inches. So you can’t really trust it,” said angler Mike Slauson. “I’ve never seen a freeze like this.”

In the past week alone, more than 40 anglers from a half-dozen different spots have required rescue by hovercraft. The ice they thought was firm and secure broke off and floated away from shore.

While Mille Lacs might appear frozen, it’s anything but static. Huge parcels of ice are constantly moving and shifting, creating massive piles of ice.

“As the wind conditions change and the ice shifts then they get separated from shore and can’t get back,” said Mille Lacs County Sheriff Brent Lindgren.

The shifting ice cover is keeping many resorts from getting rental houses onto the lake during the all-important holiday season. And when they sit on shore, it’s lost revenue.

“As you think conditions are safe, it’s ever changing out here,” said Lindgren.

Lindgren wants to get the word out before the holiday rush heads north and unsuspecting anglers find themselves stranded, unable to reach shore.

It’s recommended that anglers call resorts to find out the latest ice conditions and where cracks have opened up. Finally, Lindgren says never go out without a cell phone, preferably one equipped with GPS, so if a you do become stranded you can call for help and identify your location.