Here's a thought to keep you warm amid a furious cold snap — it's a great time for icewine.

Frigid temperatures in December had Niagara icewine growers harvesting from the vine much earlier than normal, says Debra Inglis, the director of the Cool Climate Oenology and Viticulture Institute, which does research for the Canadian grape and wine industry.

"We're anticipating a fantastic icewine yield and quality this season," Inglis said.

The key to icewine harvesting is a temperature sweet spot — anywhere between –10 C to –12 C. That's when the sweetness and flavour of the grapes is optimal, Inglis said.

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Many icewine producers harvest by hand, plucking grapes from the vine. (Pillitteri Estates Winery)

Generally, the Niagara region (which is a powerhouse in Canadian wine making) wouldn't see those temperatures until well into January or later. This year, temperatures started plummeting that low around Dec. 14 and 15, making for an early push to pluck grapes off the vine.

"It's not often we can get the grapes off before Christmas, or before New Year's," Inglis said.

And it's a good thing that most wine makers will have them off the vine by now — as it's even too cold in southern Ontario right now to harvest icewine, said Brian Schmidt, a winemaker with Vineland Estates Winery.

"When it's too cold it actually makes it harder for us to harvest," he said.

When temperatures dip below –12 C, the yield from the grapes becomes too low, and the wine is difficult to enjoy, Schmidt said. Temperatures have been well below that, with a low of –16 C in Vineland today (and an even chillier –21 C in Hamilton).

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Ted Scube, of Scube Family Farms, drives his harvester in Niagara-on-the-Lake, Ont. (Dave Chidley/Canadian Press)

"That's really more or less the beauty of where we grow grapes here in the Niagara Peninsula," Schmidt said.

"Some of the other areas like Lake Erie North Shore, Prince Edward County, don't necessarily have the same benefits, but because we're between the two large bodies of water Lake Erie and Lake Ontario, we have somewhat of a moderating effect between those two."

While the harvest is in good hands, worries about the health of the grape vines themselves are creeping in, Inglis said. Temperatures under –23 C run the risk of damaging the vines, and a replanted vine can take four to five years to get back to its full production — something growers can ill afford.

"We certainly hope we don't continue with these extreme cold temperatures," she said.

Thankfully, some relief is on the horizon. After days of extreme cold alerts, Environment Canada is calling for warmer temperatures hovering closer to the freezing mark on Sunday.

adam.carter@cbc.ca

With files from Laura Clementson