Excessive Heat — Lyon, Iowa

2025-07-27 to 2025-07-28 · Lyon, Iowa

Event narrative

Dangerous heat index readings reached an afternoon peak on July 27 as high as 116 degrees 4 miles southwest of George, 114 degrees 5 miles south-southwest of Ellsworth, and 110 degrees near Larchwood.

Wider weather episode

Beneath an expansive and strong, flat ridge aloft, extreme surface-based moisture returned near a diffuse warm frontal boundary on July 26 and lasted into the afternoon of July 28. While this moisture and heat would eventually fuel the derecho during the evening hours of July 28, dangerous heat indices from 105 to 120 degrees were common.

Source: NOAA Storm Events Database, event_id 1288607. Narrative written by the NWS forecast office that issued the report.