Argentina's 2019/20 wheat harvest is expected at 19.8 million tonnes, the Buenos Aires Grains Exchange said in its weekly crop report on Thursday, citing bad weather as the reason for cutting its previous 21 million-tonne forecast. "Toward the center and south of the agricultural belt, the season has progressed practically without rains of considerable magnitude, and with temperatures below medium levels, which has compromised crop development," the report said.

"Widespread frost and hailstorms have been recorded in areas where crops had been showing better performance, considerably affecting their condition," it said. Argentine wheat harvesting has begun in northern areas centered in the province of Salta, where yields have been favourable, the report added. After advancing 3.6 percentage points during the week, corn planting had reached 24.2% of expected area, the report said.

The exchange last month said it expects a 2019/20 corn harvest of 50 million tonnes. The Rosario grains exchange on Wednesday cut its corn crop forecast to 47.5 million tonnes from a previous view of 50 million tonnes, citing dryness and policy uncertainty ahead of the Oct. 27 presidential election. President Mauricio Macri, a free-markets proponent elected in 2015 with wide support from farmers, is expected to lose to challenger Alberto Fernandez, whose Peronist party has traditionally favoured higher grains export taxes and more government intervention in the economy.