The impact to crops, and the roads to transport them could lead to food shortages and higher supermarket prices for essentials in the midst of a cost of living crisis.

With a third consecutive La Nina underway a wet harvest spells trouble for the cherry season, while havoc has also been wreaked on grain crops and transport routes have been destroyed or are still underwater.

The impact of La Nina was evident last season with a report by RaboBank estimating Australia's total cherry production for 2021/22 was down 15 per cent on the previous year.

This year isn't looking much different with crops impacted by floods, cold weather or high rainfall.

In Victoria's central highlands family-owned cherry farm Blackwood Orchards is assessing the flood damage to their cherry crop.

Owner Colin Pickering said at least 30 of their trees were lost.

"A lot of trees are struggling because they're sitting in wet ground. The season has been abnormally cold, so the fruit isn't ripening as quickly as it normally does," Mr Pickering said.

"The quantity is going to be down. The quality is probably going to be impacted too. Because with continual rain as the cherries get closer to maturity they tend to split. so that'll affect quantity as well, because we have to throw them away."

With grain crops also impacted, the full extent of the damage to food supply won't be known until rain events ease.

NSW Farmers grains committee chair Justin Everitt the quality of the grain harvest would be diminished by the record breaking rains.

"We've had plenty of crops lost to the amount of water going through them," Mr Everitt said.

"Its been such an expensive crop to grow this year, input costs have gone through the roof, it's going to be hard to break even this year, and if we do make a profit it will be minimal."

Mr Everitt is now turning his mind to flood recovery, with road damage of particular concern.

"There's roads washed away, then you've got to try and fix it without a surplus income," he said.

"The road I'm on has become the drain, water runs down the middle of it. Everyday you're driving through flood waters to check paddocks and animals, that gets to you after a while."

Mr Everitt is not alone, with widespread flooding interrupting supply routes through NSW and Victoria as heavy rain continues to fall.

Major highway closures, including the Newell, Sturt and Hamiliton highways, have limited heavy vehicle access between regional and metropolitan areas.

The extent of the damage is unknown, particularly where roads remain submerged in flood waters.

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Transport Workers Union NSW/ACT branch secretary Richard Olsen said the linehaul roads between major cities and towns was in chaos.

"We're driving kilometres in different directions because of the closure of the roads, the degradation of the roads and some roads have been virtually washed away," Mr Olsen said.

"So either freight is not getting through or they have to divert hundreds of kilometres to get around particular areas."

Regional and rural areas rely on freight trucks to access groceries, fuel and other basic supplies.

"It's all forms of freight coming into regional and country towns, it all comes in by roads," Mr Olsen said.

"Everything is held up. The linehaul between major cities and towns is in chaos at present. We'll find that it will be weeks, if not months, before this all returns to normal.

"Our drivers are very concerned about what's going to happen next week after this next lot of rain, because we all know we can't take any more and this will only lead to worsening conditions on our roads."