This winter has brought some extreme weather with record-breaking bitter cold, freezing rain and ice, and snow levels many states haven’t seen in decades. Chicago, Detroit, and Cincinnati have seen more snow than they typically get for the entire season, and winter isn’t over yet.

The Midwest is seeing unusually cold temperatures, including cities such as Indianapolis, which is dealing with its coldest winter since 1979, according to the National Weather Service.

So, it should come as no surprise that the Great Lakes, forming the largest group of freshwater lakes on Earth, are completely covered in ice. The last time they came this close to being completely frozen was in 1994, when 94 percent of the lakes’ surface was frozen.

The Environmental Research Lab in Ann Arbor reported that as of Thursday, ice extended across 88 percent of the lakes.

Portions of the lakes that hold close to one-fifth of the worlds freshwater harden quite frequently during the winter. The Coast Guard’s fleet of icebreaking ships stay busy nearly every winter clearing paths for cargo vessels, delivering essentials such as oil for heat, salt for roads, and coal.

However, climate change scientists have recorded the average ice cover recede by 70 percent. But this season has changed all of that, trumping those previous years’ trends as winter arrived early, and with a vengeance.

“That arctic vortex came down, and the ice just kept going,” said George Leshkevich, a physical scientist with the federal lab in Ann Arbor, MI.

But there are benefits to this big freeze–first, it limits evaporation, which helps bring water levels up to where they were in the 1990s. And second, heavy ice can help the fish population by protecting their eggs from predators.

Another benefit to the deep freeze is that the Apostle Islands National Lakeshore in Wisconsin is allowing visitors to plod across Lake Superior to see and explore the incredible ice formations in the caves that surround the lake. It’s the first time in five years the lake surface has been firm enough to allow passage. And the needle-like hoarfrost crystals sprinkled across sheets that dangle from cave ceilings like giant chandeliers are something to see this winter.

“Seeing them like this is almost a once-in-a-lifetime experience,” Superintendent Bob Krumenaker said.

Still, the Coast Guard icebreaker crews are exhausted, putting in four times the average work hours required during a normal winter season. If this keeps up, crews could be working until mid May to get necessary supplies inland.

Image via YouTube