Christian leaders throughout the country led the special prayers in solidarity with farmers whose crops and livestock have been devastated by the "big dry".

"We're praying for rain, that God might bless us with rains," said Archbishop Philip Wilson, president of the Australian Catholic Bishops Conference.

"And (we are) also praying in solidarity with the people who are affected directly by all of this and who are suffering in their lives because of the drought.

"I think that it's good for the farmers to know that people who aren't directly involved in agricultural work are aware of the struggles they're having at the moment."

The president of the New South Wales Farmers Association, Jock Laurie, said that while crops had already been lost in large swathes of the state, of which Sydney is the capital, good rains would boost morale.

"Obviously rain now won't do much good in many parts of the state, but in other parts of the state it certainly will do some good and grow some pasture for stock feed," he said.

"I think it just shows that city people really are starting to get a very good understanding of the impact it's having on rural communities," he said.

Suicide rates in farming communities have soared as the relentless six-year drought has taken its toll on the world's driest inhabited continent, mental health groups have reported.

The government has called the drought the worst in a century and warned that it could cut farm production nationwide by 20 percent.

The central bank, the Reserve Bank of Australia, said the loss of production would directly cut GDP growth by about half a percentage point.