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.
Every event with a place to put it; 11 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS FSD wrote it up.
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.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Sioux Falls, SD wrote its last area forecast discussion before the first event at Jul 27, 5:21 AM CST, 5 hours 39 minutes earlier.
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</html>The national radar mosaic for the moment the first event began.
11 excessive heat. Local standard time, as filed.
Dangerous heat index readings reached an afternoon peak on July 27 as high as 116 degrees near Alta, 109 degrees in Storm Lake, and 108 degrees near Rembrandt.
Dangerous heat index readings reached an afternoon peak as high as 116 degrees near Marcus and Cleghorn, and 109 degrees at Cherokee.
Dangerous heat index readings reached an afternoon peak as high as 106 degrees near Spencer.
Dangerous heat index readings reached an afternoon peak as high as 113 degrees near Terril, 112 degrees 7 miles southwest of Milford, 110 degrees 3 miles south-southeast of Lake Park, and 108 degrees near Wahpeton.
Dangerous heat index readings reached an afternoon peak as high as 117 degrees near Battle Creek and 116 degrees at Ida Grove.
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.
Dangerous heat index readings reached an afternoon peak on July 27 as high as 119 degrees at Sutherland and 115 degrees near Hartley.
Dangerous heat index readings reached an afternoon peak on July 27 as high as 115 degrees 4 miles southeast of May City and near Ashton, 108 degrees near Sibley, and 106 degrees at May City.
Dangerous heat index readings reached an afternoon peak on July 27 as high as 120 degrees near Remsen, 119 degrees near Akron, 118 degrees near Westfield, and 111 degrees at Le Mars.
Dangerous heat index readings reached an afternoon peak on July 27 as high as 119 degrees at Hawarden, 113 degrees near Hull and Sioux Center, and 108 degrees near Maurice.
Dangerous heat index readings reached an afternoon peak as high as 120 degrees 6 miles east of Pierson, 118 degrees at Moville, 114 degrees in Sioux City, 112 degrees in Sergeant Bluff, and 108 degrees near Danbury.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2025Every state in 2025This day in weather historyWarnings in Iowa, July 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 1288602, 1288603, 1288604, 1288605, 1288606, 1288607, 1288608, 1288609, 1288610, 1288611, 1288612.