The heaviest rains in years have fallen across parts of Australia's east coast, bringing relief to some struggling livestock farmers, though experts say the showers are not likely to break a drought that has crippled the country's grains sector.

Australia's Bureau of Meteorology said some parts of the state of New South Wales received nearly 100mm of rain over Sunday.

The rainfall was particularly welcome in towns such as Bourke, 800km northwest of Sydney, where people had to start drinking groundwater in April.

Groundwater, also called bore water, is sometimes contaminated by minerals or chemicals as it seeps into aquifers below the earth's surface.

"This much-needed rain will certainly bring some much-needed relief and smiles across the country," said Oliver Gordon, a resident of Bourke.

More rains will be needed though, to break a drought that has gripped a swathe of Australia's southeast for three years, turning pastures brown and forcing ranchers to buy expensive feed grains to keep their herds alive.

Analysts said the rains may have come too late to save the grain harvest, set to begin within weeks, although the moisture will help cattle and other livestock graziers.

Wheat production is expected to fall well below 20 million tonnes, more than 22% below the ten-year average.

With many agricultural producers battling to stave off bankruptcy, Australia's conservative government has been forced to offer grants and cheap loans to farmers.

Australia's Deputy Prime Minister Michael McCormack warned that the impact of the drought would likely continue for years.

"It has settled the dust. It's going to top up some dams. A bit of a green sheet across those very dry areas - but it's not going to solve the drought," he told reporters in Melbourne.

"The drought is going to take many months and indeed years to recover from."