PRAIRIE DU SAC, Wis. -- Workers at Wollersheim Winery in Prairie Du Sac braved freezing temperatures to make a rare kind of wine.

Pickers at the winery said working in cold temperatures is part of making ice wine.

"Ice wine is kind of the ultimate wine. It's very sweet; it is a sipping wine; it could be dessert by itself," said Philippe Coquard, a winemaker at Wollersheim Winery.

Coquard said that ice wine owes its sweet taste to the cold conditions.

"You want a temperature cold enough to freeze the water in the grapes," he said. "Actually, to qualify as ice wine, it has to be picked frozen and pressed frozen."

The grapes used are of the Saint Pepin variety, which is native to Wisconsin and hearty enough to stand up to the state's winters.

"The picking this time of the year is a lot slower than it would be in September. The grapes are very frail, they could fall, so you want to go slow and get everything you can," Coquard said.

While frost is good for ice wine, Coquard said this year's wet fall is not.

"For two weeks in September we got 2 inches of rain and it kind of, not ruined the year, but we didn't finish on a high note like we were expecting," he said.

Still, Wollersheim Winery expects to produce just less than 200 half-sized bottles, which go on sale next October.

Those who buy a bottle will taste a recipe that took five years to perfect before the first vintage sold last year.

"Very few wineries in the world are able to make ice wine," Coquard said.

Coquard said that last year's vintage is available now at Wollersheim for almost $50 for a half-bottle.