(Wine-Searcher) - The first grapes picked in 2015 were from last year's vintage but, for Ontario's ice wine makers, it's worth the wait.

The cold wintry weather in Ontario might be causing most residents to burrow down into the blankets, but for others it’s a sweet time of year.

Winemakers in the Niagara Region have embraced Ontario's deep freeze, and began harvesting the 2014 crop of ice wine grapes this week. A sustained cold snap provided the perfect window to harvest and press the wines.

"The wind is pretty brutal, but it's rare we get to do this during the day," Paul Speck, president of Henry of Pelham, told Niagara This Week, just hours after the winery started to haul in its estimated 150 tonnes of Riesling, Cabernet Franc and Vidal grapes. "We’re going to go around the clock to get this done."

The season starts with netting the grape vines in the autumn, to protect the grapes from being devoured by birds. Grapes are left on the vine until a sustained temperature of -8°C (-17.6°F) or lower is reached, usually sometime between December and February. During the time between the end of the growing season and harvest, the grapes dehydrate, concentrating the juices and creating the characteristic complexities of ice wine.

Grapegrowers and wineries carefully watch the weather, looking for an optimum stretch of temperatures between -10°C and -12°C. This range will produce very sweet juice in the range of 35 to 39 degrees Brix. Typically, a period of at least six hours is needed to harvest and press the grapes – usually during the night.

While still frozen, the harvested grapes are pressed, leaving most of the water behind as ice. Only a small amount of concentrated juice is extracted. Juice yields for ice wine grapes are much lower than for table wines.

The juice can be difficult to ferment. High sugars can create a hostile environment for the yeast, and fermentation stops early, leaving relatively low alcohol and high sugar levels in the finished wine.

About 90 per cent of the grapes grown on 17,000 acres of vineyards in Ontario are used for commercial winemaking, including about 7 percent destined for ice wine production.

"Approximately 3600 tonnes have been left hanging in the province for ice wine, which may produce between 540,000 and 576,000 liters," said Bill George, chair of the Grape Growers of Ontario.

Growers in Finger Lakes have also been picking frozen grapes, but quantities are smaller than last year's bumper harvest. Many growers didn't leave any grapes on the vine this year, as the weather earlier in the year had already overstressed the vines. However, there won't be any shortage as most wineries still had ice wine from the 2013 vintage on hand.

Germany, the spiritual home of ice wine, has also had a good year, with harvesting taking place just before New Year's Eve. Grapes were picked in the Mosel, Franconia and Baden, with quality reportedly excellent and quantities healthy, too.