Roughly four of every 10 acres of corn and soybeans in Iowa “was impacted” by a fast-moving, intense windstorm, said Gov. Kim Reynolds on Tuesday. Radio Iowa quoted the governor as saying the estimate of 10 million acres affected “is really an early estimate. Some of the photos have just been devastating.”

There were widespread reports of flattened grain fields and damage to grain bins. In Luther, in central Iowa, winds toppled and mangled part of a grain elevator. Separately, Heartland Co-op, a grain marketer based in West Des Moines said 21 of its facilities “sustained serious damage…Several locations were rendered inoperable and we are making contingency plans for managing the fall harvest.” Heartland has dozens of grain elevators in Iowa.

From 200 million to 400 million bushels of corn may have been lost due to storm damage from eastern Nebraska through Iowa and into northern Illinois and northern Indiana, said Arlan Suderman, chief commodities economist for trader StoneX Group, based on counties with reports of high winds and collectively containing 17.5 million acres of corn. “Perhaps the bigger concern is all the lost storage right ahead of harvest,” said Suderman on social media.

The USDA was to release its first forecast of the fall harvest today at noon ET. The August crop report, based on conditions at the start of the month, is regarded as one of the most important reports of the growing season.