A county is generally qualified as a natural disaster area if it has suffered severe drought for eight consecutive weeks. Farmers are then eligible for low-interest emergency loans from the Department of Agriculture.
As of Tuesday, 61 per cent of land in the lower 48 states was experiencing drought conditions -- stretching from Nevada to South Carolina -- the highest percentage in the 12-year record of the US Drought Monitor.
The parched conditions come after some areas of the United States suffered record-setting heat waves, killer storms and blazing wildfires.
In America's Corn Belt, the prognosis for farmers is grim as fields and pastures become drier by the day.
"In the hottest areas last week, which were generally dry, crop conditions deteriorated quickly," CNN quoted Rich Tinker, author of the Drought Monitor as saying.
He says 30 per cent of the corn crop in the 18 primary corn-growing states is now in poor or very poor condition, up from 22 per cent the previous week.
Half of America's pastures and ranges are in poor or very poor condition, up from 28 per cent in mid-June, he says.
The past 12 months have been the warmest the United States has experienced since the dawn of record-keeping in 1895, the National Climatic Data Center said earlier this week.