Bureau of Meteorology senior forecaster Richard Carlyon said west Wimmera could receive between 60mm and 100mm on rain over the next few days, while the east Wimmera could receive between 100mm and 200mm.

He said the rain would be heaviest overnight on Thursday and would continue throughout the day on Friday and Saturday.

He said it should ease by Sunday morning.

“This is an extreme event and we have issued flood warnings and severe weather warnings for the entire state,” he said.

Mr Carlyon said the average rainfall for summer in the region was about 100mm.

“It is possible some towns will get their total summer rain in two days,” he said.

Farmers were racing against the clock earlier this week, trying to get as much of their crops harvested before the rain.

Murra Warra farmer and Victorian Farmers Federation president David Jochinke said the forecast was devastating.

“We’ve gone through so much this year already and we’ve put in so much work to get to where we are now,” he said.

“We’ve battled mice, a dry winter and frost and then to get hit with this, it’s devastating.”

Mr Jochinke said the rain could shatter legumes and canola and ruin barley and wheat.

“The worst thing about heavy rain is that you can’t insure against it unless you have multi-peril crop protection and not many farms do.”

Mr Jochinke said no farmer would ever expect to bit hit with this much rain in December.

“I’ve heard it referred to as a one-in-30 year event and it’s just a shame that it will occur right at the end of the season,” he said.

Wild weather had already caused havoc on some parts of the region this harvest, after thunderstorms went through the Wimmera at the weekend. 

At Banyena, farmer Chris Drum said a savage hail storm had flattened crops, with hail stones bigger than golf balls. 

“It probably hit three farms really badly in a strip about five kilometres wide – it flattened canola,” he said.

Mr Drum said the region was now on full alert for the upcoming rain.

“The last lot of storms were very patchy and many people missed out,” he said.

“This week it looks like Armageddon, we’re definitely at risk of crop downgrades.”

Member for Lowan Emma Kealy said it was devastating for farmers to be hit with natural disasters that were completely out of their control. 

"I was speaking to a Wimmera grower who simply won't be able to harvest his crop before the rain comes through,” she said.

“There might be grain worth $2 million that they can't get off in time, but that is the reality of farming and it will be difficult for those farmers who have big losses." 

"It is a heartbreaking blow and we need to look out for our growers in this time to make sure they are provided with all the support they need."

Wimmera Catchment Management Authority chief executive David Brennan said the region’s waterways were fairly full already after two years of above average rain.

“With rain already over the past few weeks and predictions of more summer rain, it is likely that we will get a fair bit of moisture in the catchment,” he said.

“A number of our lakes and wetlands are not full at the moment, but over the next period, we could see the catchment fill.”