For the 2015-16 season, the wheat harvest in Australia may reach 23.6 million tonnes, said the Australian Bureau of Agricultural & Resource Economics & Sciences. In the light of El Nino possibly affecting yields in the country's east, the volume fell from 24.4 million tonnes anticipated in March.

A year earlier, wheat recorded 23.7 million tonnes in volume while in 2013-14, it was a higher 25.3 million tonnes.

As Australia's wheat harvesting is set to commence in October, Peter Collins, a manager for agricultural commodities with Abares, remarked the difficulty of comprehending the El Nino effect "this early". 

"The timing of rainfall is very significant. So it is possible to have below-average rainfall, but if you get it at just the right time, then the effect is lessened," Collins told Bloomberg.

El Nino's unpredictable patterns means that outlook for Australian winter-grain output is relatively uncertain, according to the National Australia Bank Ltd., as the local growing season is expected to be troubled by continual dryness. The climatic phenomenon is generally notorious for suppressing wheat yields below trend, the MDA Weather Services said. It is also disruptive enough to induce a potential 1.4% reduction in the world's wheat production, according to the United Nations' Food & Agriculture Organization.

Affected regions in Australia include the northern and eastern areas of New South Wales, where farmers may harvest 6.2 million tonnes of crops from 6.3 milllion tonnes a year ago, as well as south Queensland and eastern Victoria facing a drier winter.

However, a different outcome is projected for Western Australia. Abares believes that the nation's largest harvest there may reach 9.3 million tonnes, compared to 8.9 million tonnes a year ago. In addition to surviving the less severe effects of El Nino, the state could welcome an unusually wetter season during June to August this year.

On a global scale, wheat production is expected to drop to 718.9 million tonnes in 2015-16, compared to 726.5 million tonnes a year earlier. The USDA attributed the decline to smaller harvests in Russia, Ukraine and the EU.

The agency also forecasts a volume of 26 million tonnes for wheat in Australia, the world's fifth biggest exporter of the crop.