The condition of the corn and soybean crops nationwide took a beating from derecho damage in Iowa and droughty weather in the Midwest during August, said the USDA in an assessment on Monday. The Crop Progress report listed 62% of corn and 66% of soybeans in good or excellent condition, compared with 72% of corn and 73% of soybeans in those categories at the start of month.

In Iowa, the No. 1 corn state, 45% of the crop rated as good or excellent this week, down by 28 points since the first days of August. The Aug. 10 derecho flattened cornfields for miles, with the heaviest damage from central Iowa to the Mississippi River. The USDA said 25% of the Iowa crop was in poor or very poor condition, twice the national rate, and 60% of the state was in moderate to extreme drought.

In early August, the USDA estimated the U.S. corn harvest would be a record 15.3 billion bushels and the soybean crop would total 4.4 billion bushels, the second largest on record. The FAPRI think tank says derecho damage in Iowa would reduce the U.S. total by 203 million bushels, but the crop would still be the largest ever.

With the latest drop in crop ratings by USDA, corn would average 175 bushels an acre and soybeans 51.6 bushels nationwide, said Arlan Suderman, chief commodities economist for StoneX Group, on social media. Suderman’s figures suggest a smaller harvest than USDA forecast on Aug. 12, when it estimated the corn yield at 181.8 bushels an acre and soybeans at 53.3 bushels an acre.

The weekly Drought Monitor said drought stretched across Iowa into northern Illinois, northern Indiana, southern Michigan, and central and northern Ohio. More than 12% of the nine-state region was in drought, most of it moderate, an increase of 4 points in a week.