Corn plants were curling up tightly in the mid-day heat last week on Mason Hoffman’s farm in Palo Alto County, where rainfall continued to be sparse even as showers brought long-awaited relief to much of Iowa.

“Every day you’re seeing more and more spots roll up,” Hoffman said June 24. “Even the good ground is starting to show stress.”

Ninety-five miles southwest of Hoffman’s farm, a storm system rattled Shelby County farmer Sam Kenkel ...