Alert archive / South Dakota / Severe Thunderstorm Warnings in 2026
Severe Thunderstorm Warning 85, NWS Sioux Falls, SD
NWS Sioux Falls, SD issued this severe thunderstorm warning at May 31, 2026, 9:43 PM CDT for Clay County, Union County, South Dakota; Plymouth County, Iowa. It was in force for 47 min. 1 report came from inside the area while it was in force.
The area
The outline as issued, with what was reported inside it.
The facts
- Issued
- May 31, 2026, 9:43 PM CDT (02:43 UTC)
- Expired
- May 31, 2026, 10:30 PM CDT
- In force
- 47 min
- Issued by
- NWS Sioux Falls, SD
- Area
- Storm-based polygon
- Tornado
- Possible
- Hail
- 1.25 in
- Wind
- 50.0 mph
Counties Plymouth County, IA, Clay County, SD, Union County, SD
The radar
The Sioux Falls radar (KFSD), 83 km from the middle of the area, began a volume at 02:44 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
What was reported inside it
| Time | Report | Where | Remark |
|---|---|---|---|
| May 31, 10:05 PM CDT | HAIL 1 | 10 S Alcester, SD | Most hail was pea to nickel sized, but a few were quarter sized. Looked like a wall cloud was about 3 to 4 miles to the west. |
Local storm reports filed while the alert was in force, from inside its polygon or its counties.
Did it verify
Verified. The Iowa Environmental Mesonet's Cow matched one storm report to this severe thunderstorm warning; the first came 22 minutes after it went out.
Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.
The watch it was issued in
The SPC watch in force over the same counties when this warning went out.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| May 31, 9:38 PM CDT | Severe Thunderstorm Watch | SPC | 4 hr |
The nearest sounding before it
Omaha, NE (KOAX), launched 00:00Z, 2.7 hours before the alert went out and 173 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 1417 J/kg
- Mixed-layer CIN
- -10 J/kg
- Mixed-layer LCL
- 1719 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 47 m²/s²
- 0-3 km storm-relative helicity
- 152 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 2.1
The text
As transmitted.
940 WUUS53 KFSD 010243 SVRFSD IAC149-SDC027-127-010330- /O.NEW.KFSD.SV.W.0085.260601T0243Z-260601T0330Z/ BULLETIN - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Warning National Weather Service Sioux Falls SD 943 PM CDT Sun May 31 2026 The National Weather Service in Sioux Falls has issued a * Severe Thunderstorm Warning for... Northwestern Plymouth County in northwestern Iowa... Southeastern Clay County in southeastern South Dakota... Union County in southeastern South Dakota... * Until 1030 PM CDT. * At 943 PM CDT, a severe thunderstorm was located near Union Grove State Park, or near Vermillion, moving east at 25 mph. HAZARD...Half dollar size hail. SOURCE...Radar indicated. IMPACT...Damage to vehicles is expected. * This severe thunderstorm will be near... Union Grove State Park around 950 PM CDT. Akron around 1005 PM CDT. Other locations impacted by this severe thunderstorm include Westfield. PRECAUTIONARY/PREPAREDNESS ACTIONS... Remain alert for a possible tornado! Tornadoes can develop quickly from severe thunderstorms. If you spot a tornado go at once into the basement or small central room in a sturdy structure. For your protection move to an interior room on the lowest floor of a building. To report severe weather, contact your nearest law enforcement agency. They will send your report to the National Weather Service office in Sioux Falls. Torrential rainfall is occurring with this storm, and may lead to flash flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 4276 9697 4298 9700 4307 9654 4266 9652 TIME...MOT...LOC 0243Z 261DEG 20KT 4287 9687 TORNADO...POSSIBLE HAIL THREAT...RADAR INDICATED MAX HAIL SIZE...1.25 IN WIND THREAT...RADAR INDICATED MAX WIND GUST...<50 MPH $$ SG
3 follow-up statements
586
WWUS53 KFSD 010302
SVSFSD
Severe Weather Statement
National Weather Service Sioux Falls SD
1002 PM CDT Sun May 31 2026
IAC149-SDC027-127-010330-
/O.CON.KFSD.SV.W.0085.000000T0000Z-260601T0330Z/
Plymouth IA-Clay SD-Union SD-
1002 PM CDT Sun May 31 2026
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1030 PM CDT
FOR NORTHWESTERN PLYMOUTH...SOUTHEASTERN CLAY AND UNION COUNTIES...
At 1002 PM CDT, a severe thunderstorm was located near Union Grove
State Park, or 11 miles northeast of Vermillion, moving east at 25
mph.
HAZARD...60 mph wind gusts and quarter size hail.
SOURCE...Radar indicated.
IMPACT...Hail damage to vehicles is expected. Expect wind damage to
roofs, siding, and trees.
This severe storm will be near...
Akron around 1005 PM CDT.
Other locations impacted by this severe thunderstorm include
Westfield.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
For your protection move to an interior room on the lowest floor of a
building.
To report severe weather contact your nearest law enforcement agency.
They will send your report to the National Weather Service office in
Sioux Falls.
Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.
&&
LAT...LON 4276 9696 4300 9692 4307 9654 4266 9652
TIME...MOT...LOC 0302Z 266DEG 22KT 4287 9673
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
$$
SG225
WWUS53 KFSD 010319
SVSFSD
Severe Weather Statement
National Weather Service Sioux Falls SD
1019 PM CDT Sun May 31 2026
IAC149-SDC027-127-010330-
/O.CON.KFSD.SV.W.0085.000000T0000Z-260601T0330Z/
Plymouth IA-Clay SD-Union SD-
1019 PM CDT Sun May 31 2026
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1030 PM CDT
FOR WEST CENTRAL PLYMOUTH...SOUTHEASTERN CLAY AND CENTRAL UNION
COUNTIES...
At 1019 PM CDT, a severe thunderstorm was located near Elk Point, or
7 miles east of Vermillion, moving east at 30 mph.
HAZARD...60 mph wind gusts and quarter size hail.
SOURCE...Radar indicated.
IMPACT...Hail damage to vehicles is expected. Expect wind damage to
roofs, siding, and trees.
This severe storm will be near...
Akron around 1025 PM CDT.
Other locations impacted by this severe thunderstorm include
Westfield.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
For your protection move to an interior room on the lowest floor of a
building.
To report severe weather contact your nearest law enforcement agency.
They will send your report to the National Weather Service office in
Sioux Falls.
Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.
&&
LAT...LON 4275 9692 4285 9685 4286 9653 4266 9652
TIME...MOT...LOC 0319Z 263DEG 26KT 4276 9677
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
$$
SG175 WWUS53 KFSD 010328 SVSFSD Severe Weather Statement National Weather Service Sioux Falls SD 1028 PM CDT Sun May 31 2026 IAC149-SDC027-127-010338- /O.EXP.KFSD.SV.W.0085.000000T0000Z-260601T0330Z/ Plymouth IA-Clay SD-Union SD- 1028 PM CDT Sun May 31 2026 ...THE SEVERE THUNDERSTORM WARNING FOR WEST CENTRAL PLYMOUTH... SOUTHEASTERN CLAY AND CENTRAL UNION COUNTIES WILL EXPIRE AT 1030 PM CDT... The storm which prompted the warning has weakened below severe limits, and no longer poses an immediate threat to life or property. Therefore, the warning will be allowed to expire. However, small hail and heavy rain are still possible with this thunderstorm. A Severe Thunderstorm Watch remains in effect until 100 AM CDT for northwestern Iowa...and southeastern South Dakota. && LAT...LON 4275 9692 4285 9685 4286 9653 4266 9652 TIME...MOT...LOC 0328Z 261DEG 20KT 4277 9673 $$ SG
What forecasters said that day
The local office's own words before this severe thunderstorm warning went out, 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 this severe thunderstorm warning went out at May 31, 6:55 PM CDT, 2 hours 48 minutes earlier. Its key messages:
- Isolated to scattered thunderstorms should develop late this afternoon into early evening. Large hail up to half dollar and damaging winds to 60 mph would be the main hazards. A Level 1 of 5 risk for severe storms covers most of the area for this threat.
- Similar to today, a conditional Level 1 of 5 risk for severe storms covers the forecast area Monday afternoon. The chance of development looks lower than today, but if a storm can form, large hail and isolated damaging winds could occur.
- High chances (50-80%) for rain will persist through the bulk of next week. However, severe storm chances continue to look low (near 5% or less) through next week. The better chances for rainfall appear to be Wednesday in central SD and Wednesday night into Thursday area wide.
Area forecast discussion, May 31, 6:55 PM CDT, 2 hours 48 minutes before
Area Forecast Discussion National Weather Service Sioux Falls SD Issued by National Weather Service Rapid City SD 655 PM CDT Sun May 31 2026 .KEY MESSAGES... - Isolated to scattered thunderstorms should develop late this afternoon into early evening. Large hail up to half dollar and damaging winds to 60 mph would be the main hazards. A Level 1 of 5 risk for severe storms covers most of the area for this threat. - Similar to today, a conditional Level 1 of 5 risk for severe storms covers the forecast area Monday afternoon. The chance of development looks lower than today, but if a storm can form, large hail and isolated damaging winds could occur. - High chances (50-80%) for rain will persist through the bulk of next week. However, severe storm chances continue to look low (near 5% or less) through next week. The better chances for rainfall appear to be Wednesday in central SD and Wednesday night into Thursday area wide. && .DISCUSSION... Issued at 1235 PM CDT Sun May 31 2026 An active pattern is expected over the next several days, although severe weather appears to remain a minor threat. Patchy heavy rain may play the bigger role with each event. For this afternoon and tonight, a small corridor of low level convergence and lift will focus near and just east of the James Valley. Clouds have cleared through early afternoon and temperatures have risen a touch. Along with this temperature rise is a turn in the surface winds to a more south to southwest direction vs. southeast. This is what is aiding in this low level convergence. The latest model soundings indicate something around 1500-2000 J/kg CAPE but weak, disorganized shear. This suggests severe weather should remain limited, but maybe a cell merger or two could produce a couple of updrafts strong enough to support hail to half dollar and wind gusts to 60 mph. Stronger storms will likely drift east or northeast at about 15 mph, so fairly slow moving. With this slower storm motion in mind, will need to keep an eye on the locally heavy rain potential. A handful of the latest hi-res models are showing small areas of 1-3" of rain with this development. One area to keep a closer eye on will be parts of Western Lake county, Northeast McCook and western Minnehaha where 1-3" of rain fell late last night. The question becomes what will drive development; will it be diurnal heating, which would allow updrafts to start developing around 19- 21z, or will it be the weak wave which moves into the area closer to 0-3z this evening. The latest HRRR and Nam output agree with the later start times, with the Nam indicating a stronger cap and less development, while the RRFS and RAP kick off development a little sooner with weaker capping. With the clearing that we are seeing in central SD towards the James Valley we may see some development by mid to late afternoon as destabilization is more likely. Suspect some development between about 5-6pm. One last thing to watch out for, if we can get mid to late afternoon development, the LFC are marginally low and a weak convergent boundary should be in parts of south central and southeast SD, so an isolated funnel or two will be possible. While a marginal risk for severe weather is in place for Monday, confidence in the chances of development are very low. A capping inversion may win out and for now CAPE values only running around 1000 J/kg with continued weak shear, albeit a little bit better than today. Another wave moves through Tuesday but weak shear and weak instability suggest if anything can develop severe weather is very unlikely. Wednesday into Thursday looks like the better chance for more clouds and better rainfall chances. Broad southerly warm advection looks to bring in some weak elevated instability as low pressure tracks east through ND. For now not anticipating all day rainfall but should see off and on chances Wednesday and Thursday as this low tracks by to the north. Friday into Sunday will see periodic weaker waves move through the area with a continuation of relatively weak flow aloft. This continued weaker shear environment should keep severe weather threats very limited. && .AVIATION...(For the 00Z TAFS Through 00Z Monday Evening) Issued At 651 PM CDT Sun May 31 2026 Isolated showers and thunderstorms will continue to be possible across the area through the early evening hours. Low stratus is expected to develop tonight over southwest Minnesota and eastern South Dakota, especially near and east of I-29. Highest confidence location for this MVFR to IFR stratus regarding the TAF sites will be at KFSD. Winds will turn light through the overnight hours, and this could also result in fog, though confidence is a bit lower in development. Additional showers and storms may develop Monday afternoon, but low confidence in development and location of these storms preclude mention in the TAFs at this time. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...08 AVIATION...13
Hazardous weather outlook, May 31, 1:33 PM CDT, 8 hours 10 minutes before
Hazardous Weather Outlook National Weather Service Sioux Falls SD 133 PM CDT Sun May 31 2026 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-011845- 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- 133 PM CDT Sun May 31 2026 This Hazardous Weather Outlook is for 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...This afternoon and tonight. A Level 1 of 5 risk for severe storms is in place for late this afternoon and evening. Isolated to scattered thunderstorms should develop late this afternoon between the James River and I-29, then progress eastward through the evening. A very isolated stronger storm could produce hail to half dollar and wind gusts to 60 mph. Locally heavier rain will also be possible with small swaths of one to three inches of rainfall. .DAYS TWO THROUGH SEVEN...Monday through Saturday. There is a low chance for storms again Monday afternoon. Similar to today, confidence in storm development is low. However, if storms can develop, isolated damaging winds and large hail would be the main threats. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
In the hours before
Local storm report, May 31, 7:40 PM CDT, 2 hours 3 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
740 PM CDT Sun May 31 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0733 PM Hail 4 SW Hurley 43.24N 97.15W
05/31/2026 E1.00 Inch Turner SD Fire Dept/Rescue
&&
TRMLocal storm report, May 31, 8:05 PM CDT, 1 hour 38 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
805 PM CDT Sun May 31 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0754 PM Hail 2 WNW Davis 43.27N 97.04W
05/31/2026 E1.00 Inch Turner SD Public
&&
TRMLocal storm report, May 31, 8:18 PM CDT, 1 hour 25 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
818 PM CDT Sun May 31 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0817 PM Hail Wakonda 43.01N 97.11W
05/31/2026 E0.88 Inch Clay SD Trained Spotter
&&
TRMLocal storm report, May 31, 8:23 PM CDT, 1 hour 20 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
823 PM CDT Sun May 31 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0811 PM Tornado 4 W Wall Lake 43.53N 97.03W
05/31/2026 Minnehaha SD NWS Employee
Radar confirmed tonado.
&&
TRMLocal storm report, May 31, 8:47 PM CDT, 56 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
847 PM CDT Sun May 31 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0845 PM Hail Davis 43.26N 97.00W
05/31/2026 E1.00 Inch Turner SD Emergency Mngr
&&
TRMLocal storm report, May 31, 8:58 PM CDT, 45 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
858 PM CDT Sun May 31 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0854 PM Tornado 5 NE Centerville 43.17N 96.89W
05/31/2026 Lincoln SD Storm Chaser
Tornado observed from chaser live feed.
&&
TRMThe office that day
Everything else NWS Sioux Falls, SD issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 31, 7:06 PM CDT | Tornado Warning | FSD | McCook, Minnehaha | 39 min |
| May 31, 7:08 PM CDT | Severe Thunderstorm Warning | FSD | McCook, Minnehaha | 52 min |
| May 31, 7:23 PM CDT | Severe Thunderstorm Warning | FSD | Lincoln, Turner | 52 min |
| May 31, 7:42 PM CDT | Tornado Warning | FSD | McCook, Minnehaha | 23 min |
| May 31, 7:50 PM CDT | Tornado Warning | FSD | Turner | 40 min |
| May 31, 7:54 PM CDT | Severe Thunderstorm Warning | FSD | Minnehaha | 51 min |
| May 31, 8:03 PM CDT | Tornado Warning | FSD | Minnehaha | 42 min |
| May 31, 8:21 PM CDT | Severe Thunderstorm Warning | FSD | Lincoln, Turner | 54 min |
| May 31, 8:29 PM CDT | Tornado Warning | FSD | Lincoln, Turner | 46 min |
| May 31, 8:42 PM CDT | Severe Thunderstorm Warning | FSD | Clay, Lincoln, Turner, Yankton | 63 min |
| May 31, 8:43 PM CDT | Tornado Warning | FSD | Minnehaha | 32 min |
| May 31, 8:57 PM CDT | Tornado Warning | FSD | Lincoln, Turner | 35 min |
| May 31, 9:11 PM CDT | Tornado Warning | FSD | Clay, Union | 49 min |
| May 31, 11:08 PM CDT | Severe Thunderstorm Warning | FSD | Union | 52 min |
| May 31, 11:44 PM CDT | Severe Thunderstorm Warning | FSD | Cherokee, Plymouth, Woodbury | 46 min |
| Jun 1, 12:24 AM CDT | Severe Thunderstorm Warning | FSD | Woodbury | 51 min |
Nearby
Severe Thunderstorm Warnings in South Dakota, 2026Severe Thunderstorm Warnings in Iowa, 2026Every severe thunderstorm warning in 2026
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.