At least 70 millimetres of rain is predicted to fall on Friday and Saturday, but two days of thunderstorms could see as much as 400ml fall over the 48-hour period.

Chaotic weather has already wreaked havoc for growers across the region, forcing many farmers to adopt contingency plans to salvage damaged crops.

BOM duty forecaster Mohammed Nabi said the combination of a lingering high pressure system, unseasonably humid conditions and a rapidly approaching cold front lead to the massive predictions.

“We've seen consistently warm temperatures across NSW and Victoria for the last couple of weeks,” he said.

“A cold front is moving south very quickly, and it is interacting with a high level of humidity in the areas.

“It is fairly common to have cold fronts at this time of year, but generally we wouldn't see this level of humidity until February.”

The massive storm front, which BOM extreme weather desk senior meteorologist Scott Williams described as “uncharted territory", has placed farmers under significant stress.

Henty grower Damien Schneider said almost everyone he knew had been working almost around the clock since Monday, with many looking to recruit contractors to help salvage crops before they were heavily compromised or destroyed by the impending downpour.

“We've been going for three days now, we worked from midday on Wednesday to about 4.30am on Thursday,” he said.

“It's not a forecast where we stop for a little while, this will actually destroy a lot of crops.

“It really only hit me a couple of days ago, I'm getting a bit wound up about it because there's a lot of money on the line.

“If the wheat gets degraded, you we could see a price drop of about $50 per tonne at least, which becomes a big number when we've still got more than 2000 tonnes left to do.” 

WorkSafe has also issued a warning to farmers, urging them to take care while harvesting.

Several events around the Border have had to enact contingency plans for the weather.

The Great Australian Beer Festival, which is scheduled to go head in Albury on Saturday, has been forced to truck in large marquees and umbrellas, as well as hosting corporate bookings in the Albury Entertainment Centre.