TORONTO - Producers of Ontario's renowned icewine are delighted by this week's plunge into the deep freeze, and they're finally bringing in a harvest delayed by mild temperatures.

"We got started about 9 o'clock last night,'' Debi Pratt, public relations manager of Inniskillin wines, said Wednesday from Niagara-on-the-Lake, Ont.

"We concentrated on our Cabernet Franc variety,'' said Pratt, sounding pleased.

The Inniskillin winery uses three varieties for icewine -- Cabernet Franc, Reisling and Vidal -- with Vidal being the largest volume.

Cabernet Franc and Riesling are picked first because they have a thinner skin.

Since the thicker skinned Vidal can survive longer on the vine, "we just want to get the ones that might be more susceptible to anything off flavour,'' she said.

The grapes stay on the vine until they freeze and the sugars concentrate, ideally at temperatures of -8C to -13C.

"It's been challenging,'' said Pratt. "We've had -8C, but you have to make sure that the grapes are truly frozen.''

The next few days don't look good for harvesting, she said.

"For tonight they're talking -9C. But the temperatures around it are above. Tomorrow we're back to like 1C. Saturday, though, looks like a good window at -9 again,'' she said.

The grapes can stand a bit of up and down in the temperatures.

"That's part of the process. There's a bit of dehydration in there so it really does concentrate the juice ... that's left,'' said Pratt.

Despite all the challenges this season, the harvest is on target, she said.

"If you look at it from a historical perspective, we've picked as early as Dec. 2 and as late as March 5,'' said Pratt. "An awful lot of it falls into January, in particular in mid-January.''

By March, though, dehydration begins in earnest, making for higher quality, but lower quantity.

As to the size of the harvest, Pratt said the winery preferred to wait "until we actually get it finished.''

"The Vidal grapes are looking great ... and healthy,'' she said.

Icewine is icewine only if it follows precise regulations set up in Canada by the Vintners Quality Alliance, or VQA.

Among other things, the regulations stipulate no artificial freezing.

The Niagara Peninsula is the world's leading maker of icewine and is home to most of Ontario's 69 producers. Last year, $14 million in icewine was consumed in Canada, while $11 million was exported. Total production exceeded 400,000 litres.