Excessive Heat in Osceola, Iowa

Dangerous heat index readings reached afternoon peaks as high as 108 degrees 4 miles southeast of May City and 106 degrees at Ashton on July 23.

Moisture pooled in the vicinity of a nearly stationary boundary early on July 21, which slowly worked northward as a warm front over the next two days while a large upper level ridge expanded across the Northern Plains. Most areas experienced heat index values from 100 to 115 degrees, with the most consistent and highest heat index values on the afternoon of July 23 across far southeast South Dakota, northwest Iowa, and northeast Nebraska.