''All indications are it's going to be a decent one, down to minus one or minus two, so there could be significant losses if growers aren't prepared for it,'' Central Otago Winegrowers Association president James Dicey said yesterday .
'Bud burst had ''well and truly happened'' in the Cromwell basin and crops were at a vulnerable stage, so grape growers would be on alert, he said.
''With the weather we've had this week, I can't imagine anyone will be caught unawares, but if the frost arrives as predicted, there could be significant losses.''
The Bannockburn grape grower said he expected helicopters to be out in force today as part of the frost-fighting measures.
The machines hover low over the crops, circulating the air and pushing warmer air from the inversion layer down on to the freezing ground.
The frosts are the sting in the tail of the wintry blast that brought snow to the hills, and heavy rain and gale-force winds to parts of the country.
Summerfruit New Zealand chairman Gary Bennetts, of Roxburgh, said the cold front could be a ''game-changer'' for growers.
''We had a burst in early September where we were frost-fighting six or seven nights in a row but it hasn't been too bad apart from that, up until now,'' he said.
Fruit trees bloomed earlier than usual but after that early start to the season, a few cold spells meant things had slowed down a bit again.
Orchardist Mark Jackson, of Cromwell, said stonefruit and apples were at risk from frosts. Cherries and apples were in bloom now but the rest of the stonefruit which had finished flowering was also vulnerable, he said.
Roxburgh orchardist Stephen Jeffery said fruit growers often fought frosts well into November.
''This isn't anything unusual for us. The unsettled weather just makes things a little more stressful.''
High winds on Monday did not appear to have caused any damage ''but we wouldn't want them closer to harvest time'', Mr Jeffery said.
Mr Dicey said the grape season appeared to be about a week earlier than normal.
