Rainfall totals fell away quickly with distance from the coast with Springwood collecting 38 per cent of average rain.

Reservoir levels continue to drop, with Sydney's catchments running at about two-thirds full. Warragamba, which supplies about 80 per cent of the city's water, is down about a quarter in the past year to be 71.5 per cent full as of Monday, according to WaterNSW.

Statewide, rainfall was about one-third below the average for June. For the first six months, though, the rain totals are roughly half the norm for both NSW as a whole and for the key food bowl, the Murray-Darling Basin, the bureau said.

It was also the driest January-June for both regions since 1986.

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"It's one of the driest starts to a year we've seen," said Lynette Bettio, acting head of long-range forecasting at the bureau.

'Trying season'

Farmers, such Matthew Passmore and his son Gabriel, are among those doing it tough.

Their cattle farm near Forbes in the state's central west has had little rain since last September, forcing them to bring in fodder at prices approaching $10,000 per truckload of around 30 tonnes.

"It's one of the most trying seasons for all farmer," said Mr Passmore, who has run cattle in area for almost six decades. "We've had droughts for longer periods, but not as severe - and the outlook is bleak."

"It's been a nightmare finding fodder," his son said, adding, "a lot of NSW will be very, very bad" unless decent rains come by September.

El Nino and record warmth

Odds favour drier than average conditions for most of south-eastern Australia, according to the bureau's outlook for July to September.

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The bureau said last week conditions in the Pacific were now favouring an El Nino, a weather pattern that typically results in rain shifting eastwards, drying out eastern Australia.

Along with lower rainfall than average, temperatures also tend to be higher than normal during El Ninos for much of Australia.

The year is already off to a hot start. In Sydney, the first six months were the second hottest on record - in bureau data going back to 1858 - for maximums, running 2 degrees above average and trailing only 2016.

For NSW as a whole, it was also the state's hottest January-June period for both daytime and mean temperatures, adding to the depletion of soil moisture as evaporation increased. Minimums were the sixth-highest on record.

Nationally, it's a similar story with maximums the second-warmest on record for the first six months, beaten only by 2005.

Over the past 12 months, Australia's daytime temperatures were at a record high, according to the bureau. The departure from the norm over the 1961-90 period was almost 1.5 degrees.

Farm aid

The Passmores said assistance to reduce the cost of transporting fodder would be the best way to assist farmers in their region.

Niall Blair, the NSW primary industries minister, said "almost all of NSW" was now experiencing drought conditions.

"We know the drought is hitting our farmers hard and despite some recent useful rainfall, the forecast is poor," he said.

“During the 2017-18 financial year, the NSW Rural Assistance Authority approved approximately $120 million in grants and loans to more than 2,100 primary producers," he said.

The recently announced Drought Assistance Fund providing $50,000, seven-year interest free loans had been extended to allow farmers to collect and store genetics of their herds and flocks.

Some 114 applications for the fund, totalling $5.52 million, had been received in the first three weeks of its offering, Mr Blair said.

Federal farm support has also been increased, with the Turnbull government extending the Farm Household Allowance grant from three years to four year.

“The Coalition Government has already spent more than $1.3 billion in farmer assistance and recently announced an additional $22 million for financial counselling and mental health services," David Littleproud, the federal agriculture minister, said.

According to the government, more than 7,900 farmers had accessed the FHA at a cost of $230 million dollars, shy of the estimated 27,000 farmers who may be eligible for help but have not yet accessed it.

“I urge farmers in drought not to self-assess and to contact their nearest Rural Financial Councillor,” Mr Littleproud said.