Wine grape growers in some of Australia's largest and most iconic regions say they have suffered crop losses due to unseasonable frosts, which are forecast to continue.

Overnight freezing temperatures have hit large parts of the country in recent days, with the Barossa Valley, Clare Valley and Riverland just some of the regions affected.

Temperatures dipped as low as -4 degrees Celsius in the Barossa on Monday morning and 1.5C in the Riverland. 

It follows a string of cold nights and early mornings, with temperatures dropping into the low single digits and below zero in both regions.

Fifth-generation grape grower Adrian Hoffmann, who is based in the Barossa Valley, said it was hard to estimate exactly how much crop he had lost in recent days.

"It's been quite devastating, considering we've got quite a bit of frost mitigation [strategy in place] and we've been frosted quite severely under frost fans," he said. 

"Generally once [the temperature] gets down that low, the damage is quite extensive.

Constant vigilance

In the Riverland, which is Australia's largest wine grape growing region, Michael Stivahtaris has already started counting his losses at his vineyard in Monash.

He said at least 20 per cent of his crop had been destroyed by the string of September frosts, which were caused by low winter rainfall.

The Riverland has an annual average rainfall of 250-300 millimetres but received only 50mm in the past three months.

"Unfortunately, it hasn't rained, it is very dry and we're going to be susceptible to frosts right up until the end of October unless we get some very good rain within the next week or so," Mr Stivahtaris said.

While frosts have caused Mr Stivahtaris stress, he said it would be felt by more industries further afield. 

"If you're in an area where the frost came through, any sorts of crops can be damaged: almonds, stone fruit, apricots or peaches," he said. 

Source - abc.net.au