An isolated thunderstorm developed along a slow-moving frontal boundary across northwest Iowa. Seasonally high instability (around 2000 J/kg MLCAPE) and weak shear led to very strong updrafts, producing large hail that caused significant damage to late season crops.
Every event with a place to put it. 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.
An isolated thunderstorm developed along a slow-moving frontal boundary across northwest Iowa. Seasonally high instability (around 2000 J/kg MLCAPE) and weak shear led to very strong updrafts, producing large hail that caused significant damage to late season crops.
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 Sep 22, 5:28 PM CST, 12 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD Issued by National Weather Service Aberdeen SD 628 PM CDT Mon Sep 22 2025 .KEY MESSAGES... - Scattered thunderstorms possible late this afternoon into the early overnight hours. Ping pong ball-sized hail and wind gusts to 60 mph are the main threats from the strongest storms. - A persistent seasonally warm pattern will be in place Tuesday through early next week with very small chances for precipitation. - Patchy fog possible on Tuesday morning. && .UPDATE... Issued at 623 PM CDT Mon Sep 22 2025 We continue to monitor a broken line of convection across O'Brian and Clay Counties as it slowly sinks southeast. CAMs continue to show this southern progression as well as the potential for additional development west of the current storms. && .DISCUSSION... Issued at 206 PM CDT Mon Sep 22 2025 The tail end of an exiting wave will bring a small chance for some diurnally driven thunderstorms into parts of northwest IA late this afternoon into the evening. With close to 2000 J/kg CAPE in this environment and fairly weak shear, a few severe storms will be possible. The main threats from the strongest storms would be ping pong ball-sized hail and wind gusts to 60 mph. During the evening and night-time hours a wave will move through NE and another shot for storms along the NE/SD border towards Sioux City. These storms may also produce a few stronger updrafts with weak shear and about 1500 J/kg CAPE. Once the thunderstorm threat passes tonight a ridge of high pressure will settle into northern and central SD. This will bring some cooler morning readings with at least a small chance of a few locations sneaking into the upper 40s near highway 14. With a marginally moist ground in places and light winds, some patchy fog will again be possible, with the better chances near and north of I-90. Cooler high pressure builds south and brings about a seasonally warm day on Tuesday with relatively light winds. A small corridor around highway 81 and I-29 may see some spotty diurnally driven showers Tuesday afternoon. Skinny CAPE with values less than about 300 J/kg. Fairly low confidence in this occurrence. A dry and warm pattern develops Wednesday into the weekend with very little if any chance for precipitation. One stronger wave does move by to the north on Friday and brings a nice warm nose into the area, so a very small chance for a shower or thunderstorm on Friday. With this warm nose Friday, should also prove to be the warmest with some mid and possibly upper 80s for highs. Another warm nose may sneak into the area Sunday night into Monday and bring another very small chance, but once again too low to mention. Outside of Friday, Wednesday through early next week should see highs in the 70s to lower 80s. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 623 PM CDT Mon Sep 22 2025 VFR conditions are expected over the next 24 hours at HON/FSD/SUX. The main concern will be with the initial thunderstorm activity northeast of SUX. Forecast solutions show the potential of at least PROB30/TEMPO30 from around 01-05Z this evening. There is also the potential for fog at at least HON/FSD around daybreak, so have kept the potential for 4SM BR at that time. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && UPDATE...06 DISCUSSION...08 AVIATION...06
Hazardous Weather Outlook National Weather Service Sioux Falls SD Issued by National Weather Service Aberdeen SD 437 PM CDT Mon Sep 22 2025 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-232145- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory- Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson- McCook-Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme- Yankton-Union- 437 PM CDT Mon Sep 22 2025 This Hazardous Weather Outlook is for portions of northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota, and southeast South Dakota. .DAY ONE...Tonight Isolated strong to severe thunderstorms are possible through this evening. The highest chances will be south of I-90. A few storms may become strong to severe with ping-pong ball sized hail and damaging winds up to 60 mph being the primary threats. Patchy dense fog is possible overnight into Tuesday. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Patchy dense fog is possible Tuesday morning. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. 06
The Sioux Falls radar (KFSD), 117 km away, was scanning. The volume nearest the first event began at 23:39 UTC.
4 hail. Local standard time, as filed.
An extended period of hail fell with hail up to 2 inches in diameter from 1740 to 1750 CST. Hail was still falling at dime to nickel size as of 1809 CST.
A few 2 inch hailstones fell on the north edge of Sutherland.
Several photos were received of quarter size hail in Primghar.
Quarter size hail fell for approximately 5 minutes.
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, September 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 2026-09-24. Each event’s entry at NCEI: 1292882, 1292884, 1292886, 1292890.