Severe frosts and a cold spring in the United States have damaged wheat crops and delayed corn planting.
The poor weather is threatening to slash American yields and increase the demand for Australian grain.
Market analyst Arlan Suderman, from Wichita in Kansas, says global grain prices will rise if poor conditions linger in the US.
"If the pattern holds for several more weeks, then we could be looking at a much more substantial reduction in acreage," he said.
"(This) would dramatically impact the global feed grain balance sheet and probably lead to much sharper global feed prices."
© ABC 2013
12:35 EST Heavy showers have continued over southwestern parts of Western Australia after yesterday saw some of the heaviest August rain in 100 years.