The most extensive drought in five decades intensified this week across the US midwest and plains states that produce most of the county’s corn, soybeans and livestock, a report from climate experts showed on Thursday.

Almost 30% of the nine-state midwest was suffering extreme drought, nearly triple from the previous week, according to the US drought monitor for the week ending 24 July.

Conditions in the midwest, which produces roughly three quarters of the corn and soybean crops in the world’s largest producer and exporter, worsened despite the first measurable rainfall in a month in some areas.

More than 53% of the United States and Puerto Rico are in moderate drought or worse, a record-large amount for the fourth straight week in the drought monitor’s 12-year history.

“The two-plus inches (of rain) from southern Wisconsin to northern Indiana was able to only maintain status quo. Most other areas were not as lucky,” said the drought monitor author Richard Heim of the National Climatic Data Centre.

“Pasture, rangeland, and crop condition continued to deteriorate from the Colorado high plains to the Ohio and mid-Mississippi valleys, and from Oklahoma to the Dakotas,” he said.

More than half of the country’s pastures have been rated poor or very poor by the US Agriculture Department, while the corn and soybean crops have wilted under scorching temperatures during their more vulnerable periods of pollination.

A Reuters poll this week estimated the US corn yield at 130.8 bushels per acre, the lowest in 10 years.

“This drought is two-pronged,” Fuchs said. “Not only the dryness but the heat is playing a big and important role. Even areas that have picked up rain are still suffering because of the heat.”

Light showers overnight in the southwestern midwest were too little too late to prevent further losses in the crops, while heat of 38C or higher was forecast to continue into next week, Andy Karst, meteorologist for World Weather Inc, said on Thursday.