Grape growers in the New South Wales Riverina are facing a "depressing" wait to see what damage a heatwave will reap on their crops this week.

Agriculture is the lifeblood of the community of Griffith and there are fears the extreme heatwave sweeping across south-eastern Australia could cause substantial damage.

Wine grape grower and Griffith mayor, John Dal Broi, says it's an anxious time for the community, with temperatures forecast to soar to 40 degrees today.

"With only one or two hot days the vine shuts down and... the end result is there's an effect on quality," he told the ABC.

"The other problem will be sunburn - if you see an exposed bunch that does not have enough leaf cover, they will also burn and the wineries won't like that... so the farmer cops it two ways."

With temperatures forecast to remain in the 40s for most of the week, Mr Dal Broi says there is nothing farmers can do other than try and keep water up to the vines.

He says it's not just grapes that will feel the heat.

Sorry, this video has expired Riverina Mayor nervously awaits heatwave ( Jake Sturmer )

"As a whole area, there may be an effect on our citrus because they don't like this sudden jolt of hot weather, so we may get some damage there," he said.

The heatwave comes at a particularly difficult time for growers in the region.

"In the wine grapes industry, we had in mid-November what is referred to a 'black frost' which caused an enormous amount of damage," Mr Dal Broi said.

"Tens of thousands of tonnes of wine grapes just virtually shrivelled up.

"Now we get his heatwave, a lot of farmers are saying 'what next?'"

Mr Dal Broi says it is depressing that the heatwave could damage crops just weeks out from harvest time.