Alert archive / Iowa / Severe Thunderstorm Warnings in 2026

Severe Thunderstorm Warning 53, NWS Sioux Falls, SD

May 18, 20264 counties in Iowa

NWS Sioux Falls, SD issued this severe thunderstorm warning at May 18, 2026, 5:48 PM CDT for 4 counties in Iowa. It was in force for 42 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 18, 2026, 5:48 PM CDT (22:48 UTC)
Expired: May 18, 2026, 6:30 PM CDT
In force: 42 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Damage threat: Considerable
Hail: 1.75 in
Wind: 60.0 mph

Counties Buena Vista County, IA, Cherokee County, IA, Clay County, IA, O'Brien County, IA

The radar

The Sioux Falls radar (KFSD), 137 km from the middle of the area, began a volume at 22:51 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 18, 5:49 PM CDT	HAIL 0.88	4 Sse Cherokee, IA

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

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 nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 10.8 hours before the alert went out and 184 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 871 m above ground
0-6 km bulk shear: 49 kt
0-1 km storm-relative helicity: 271 m²/s²
0-3 km storm-relative helicity: 220 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

820 
WUUS53 KFSD 182248
SVRFSD
IAC021-035-041-141-182330-
/O.NEW.KFSD.SV.W.0053.260518T2248Z-260518T2330Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Sioux Falls SD
548 PM CDT Mon May 18 2026

The National Weather Service in Sioux Falls has issued a

* Severe Thunderstorm Warning for...
  Northeastern Cherokee County in northwestern Iowa...
  Northwestern Buena Vista County in northwestern Iowa...
  Southern Clay County in northwestern Iowa...
  Southeastern O'Brien County in northwestern Iowa...

* Until 630 PM CDT.

* At 548 PM CDT, a severe thunderstorm was located near Quimby, or
  near Cherokee, moving northeast at 45 mph.

  HAZARD...Golf ball size hail and 60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...People and animals outdoors will be injured. Expect hail 
           damage to roofs, siding, windows, and vehicles. Expect 
           wind damage to roofs, siding, and trees.

* This severe thunderstorm will be near...
  Cherokee, Aurelia, and Larrabee around 555 PM CDT.
  Peterson around 605 PM CDT.

Other locations in the path of this severe thunderstorm include
Sutherland, Linn Grove and Royal.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4264 9545 4269 9571 4313 9546 4297 9499
TIME...MOT...LOC 2248Z 215DEG 40KT 4268 9558 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Meyers

3 follow-up statements

654 
WWUS53 KFSD 182301
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
601 PM CDT Mon May 18 2026

IAC021-035-041-141-182330-
/O.CON.KFSD.SV.W.0053.000000T0000Z-260518T2330Z/
Cherokee IA-Buena Vista IA-Clay IA-O'Brien IA-
601 PM CDT Mon May 18 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 630 PM CDT
FOR NORTHEASTERN CHEROKEE...NORTHWESTERN BUENA VISTA...SOUTHWESTERN
CLAY AND SOUTHEASTERN O'BRIEN COUNTIES...

At 601 PM CDT, a severe thunderstorm was located near Larrabee, or
near Cherokee, moving northeast at 45 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...
  Sutherland, Peterson, and Larrabee around 605 PM CDT.

Other locations in the path of this severe thunderstorm include Linn
Grove, Royal and Greenville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4267 9547 4274 9561 4311 9541 4300 9509
TIME...MOT...LOC 2301Z 211DEG 40KT 4281 9547 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Meyers

588 
WWUS53 KFSD 182312
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
612 PM CDT Mon May 18 2026

IAC141-182322-
/O.CAN.KFSD.SV.W.0053.000000T0000Z-260518T2330Z/
O'Brien IA-
612 PM CDT Mon May 18 2026

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN O'BRIEN COUNTY IS
CANCELLED...

The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

&&

LAT...LON 4291 9519 4276 9536 4281 9548 4291 9541
      4291 9539 4295 9539 4307 9531 4300 9509
TIME...MOT...LOC 2312Z 213DEG 45KT 4294 9527 

$$

IAC021-035-041-182330-
/O.CON.KFSD.SV.W.0053.000000T0000Z-260518T2330Z/
Cherokee IA-Buena Vista IA-Clay IA-
612 PM CDT Mon May 18 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 630 PM CDT
FOR NORTHEASTERN CHEROKEE...NORTHWESTERN BUENA VISTA AND SOUTHWESTERN
CLAY COUNTIES...

At 612 PM CDT, a severe thunderstorm was located near Linn Grove, or
15 miles southwest of Spencer In Clay County, moving northeast at 50
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...
  Royal and Greenville around 615 PM CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4291 9519 4276 9536 4281 9548 4291 9541
      4291 9539 4295 9539 4307 9531 4300 9509
TIME...MOT...LOC 2312Z 213DEG 45KT 4294 9527 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Meyers

001 
WWUS53 KFSD 182326
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
626 PM CDT Mon May 18 2026

IAC021-035-041-182335-
/O.EXP.KFSD.SV.W.0053.000000T0000Z-260518T2330Z/
Cherokee IA-Buena Vista IA-Clay IA-
626 PM CDT Mon May 18 2026

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN CHEROKEE...
NORTHWESTERN BUENA VISTA AND SOUTHWESTERN CLAY COUNTIES WILL EXPIRE
AT 630 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.

&&

LAT...LON 4291 9519 4276 9536 4281 9548 4291 9541
      4291 9539 4295 9539 4307 9531 4300 9509
TIME...MOT...LOC 2325Z 215DEG 40KT 4304 9517 

$$

Meyers

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 18, 1:01 PM CDT, 4 hours 47 minutes earlier. Its key messages:

Showers and isolated thunderstorms return to the area this afternoon this evening into tonight.
A few storms along and southeast of a Wayne to Sheldon to Windom line may be strong to severe late this afternoon into this evening. The main threat would be hail to half dollar size but storms this strong should remain very isolated and likely closer to near and east of Highway 60.
Areas of frost or freeze will be possible on Wednesday morning, with the better chances north of I-90.
Cool conditions prevail this week. Dry weather expected mid week. Another round of storms is possible Thursday through Friday.

Area forecast discussion, May 18, 1:01 PM CDT, 4 hours 47 minutes before

Area Forecast Discussion
National Weather Service Sioux Falls SD
101 PM CDT Mon May 18 2026

.KEY MESSAGES...

- Showers and isolated thunderstorms return to the area this
  afternoon this evening into tonight.

- A few storms along and southeast of a Wayne to Sheldon to
  Windom line may be strong to severe late this afternoon into
  this evening. The main threat would be hail to half dollar
  size but storms this strong should remain very isolated and
  likely closer to near and east of Highway 60.

- Areas of frost or freeze will be possible on Wednesday
  morning, with the better chances north of I-90.

- Cool conditions prevail this week. Dry weather expected mid
  week. Another round of storms is possible Thursday through
  Friday.

&&

.DISCUSSION...
Issued at 1258 PM CDT Mon May 18 2026

Early this afternoon the surface to 925 mb front was across southern
NE into southern IA. Given the marginal strength of the incoming
wave, this boundary should not lift far enough north and west
by late afternoon to get into the area. This should limit any
wind and tornado threats and keep them off to the southeast.
However, some elevated hailers will remain possible across
mainly northwest IA as elevated CAPE values ramp up to about
1000-1500 J/KG and deep layer shear is a fairly strong,
unidirectional 40-50 knots. This would be lifting a parcel from
above the stratus layer, which would likely be in about the
800-750mb layer. The better chances will be from about 5 pm to 9
pm.

After this wave pushes the remaining instability out of the area
this evening, dry and cool conditions are expected for Tuesday and
Wednesday. The only concerns on these two days will be the potential
for frost and freeze conditions, mostly north of I-90, as surface
high pressure is in place. Another weaker wave moves through the
area on Wednesday but for now this appears to bring mainly mid level
cloud cover.

The next better chance for showers and thunderstorms will come
Thursday night into Friday night. At this time severe weather looks
to remain isolated as model instability fields are hinting at 1000
J/kg CAPE or less for the most part.

Once this wave passes a warming trend should move in as flat ridging
aloft develops ahead of a deepening low pressure in the Northern
Rockies. Saturday should be mild, likely in the 70s, while Sunday
sees the better chance to warm into the 80s.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1243 PM CDT Mon May 18 2026

Widespread stratus, mai.nly IFR but occasionally MVFR, will
persist through much of the night, but gradually improve later
tonight into Tuesday morning. Scattered showers and isolated
thunderstorms will increase in coverage through the afternoon
into the early evening, then gradually diminish through the
early overnight hours. The strongest thunderstorms will be in
parts of northwest IA, with the better chance from 5 pm through
9 pm. A few of these storms could contain hail.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

DISCUSSION...08
AVIATION...08

Hazardous weather outlook, May 18, 3:31 AM CDT, 14 hours 17 minutes before

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
331 AM CDT Mon May 18 2026

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-190845-
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-
331 AM CDT Mon May 18 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...Today and tonight.

Scattered showers and isolated thunderstorms return to the area this
afternoon through tonight. A few strong to severe storms are possible
along and southeast of a line from Wayne to Sheldon to Windom. If
strong storms develop, ping pong ball sized hail and 60 mph wind
gusts are the main threats. However, locally heavy rainfall and a
tornado are possible.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Chances for showers and thunderstorms return Thursday through
Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

In the hours before

Local storm report, May 18, 4:30 PM CDT, 1 hour 18 minutes before

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
430 PM CDT Mon May 18 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0418 PM     Hail             Concord                 42.38N 96.99W
05/18/2026  E0.88 Inch       Dixon              NE   CO-OP Observer

&&

TRM

Local storm report, May 18, 5:05 PM CDT, 43 minutes before

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
505 PM CDT Mon May 18 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0450 PM     Hail             Akron                   42.83N 96.56W
05/18/2026  E0.88 Inch       Plymouth           IA   Emergency Mngr

&&

TRM

Local storm report, May 18, 5:11 PM CDT, 37 minutes before

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
511 PM CDT Mon May 18 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0502 PM     Hail             2 N Sioux City          42.53N 96.39W
05/18/2026  E0.88 Inch       Woodbury           IA   Trained Spotter

&&

TRM

Local storm report, May 18, 5:21 PM CDT, 27 minutes before

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
521 PM CDT Mon May 18 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0513 PM     Hail             7 SSE Moville           42.39N 96.03W
05/18/2026  E0.70 Inch       Woodbury           IA   Trained Spotter

&&

TRM

Local storm report, May 18, 5:42 PM CDT, 6 minutes before

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
542 PM CDT Mon May 18 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0523 PM     Hail             3 WSW Correctionville   42.46N 95.84W
05/18/2026  M1.75 Inch       Woodbury           IA   Public

            Social media picture.

&&

ak

Local storm report, May 18, 5:48 PM CDT, 0 minutes before

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
548 PM CDT Mon May 18 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0539 PM     Hail             2 N Washta              42.60N 95.71W
05/18/2026  E0.88 Inch       Cherokee           IA   Trained Spotter

&&

TRM

The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 17, 7:20 PM CDT	Severe Thunderstorm Warning	FSD	Plymouth, Sioux	28 min
May 17, 7:20 PM CDT	Severe Thunderstorm Warning	FSD	O'Brien, Osceola	26 min
May 17, 7:26 PM CDT	Tornado Warning	FSD	Woodbury	49 min
May 17, 7:32 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Cherokee, Ida, Plymouth, Woodbury	58 min
May 17, 7:47 PM CDT	Tornado Warning	FSD	Cherokee, Plymouth, Woodbury	43 min
May 17, 8:00 PM CDT	Severe Thunderstorm Warning	FSD	O'Brien, Osceola, Plymouth, Sioux	45 min
May 17, 8:03 PM CDT	Flash Flood Warning	FSD	Plymouth, Sioux	3 hr
May 17, 8:21 PM CDT	Severe Thunderstorm Warning Destructive damage threat	FSD	Buena Vista, Cherokee, Clay, Dickinson, Ida, O'Brien and 3 more	54 min
May 17, 8:26 PM CDT	Tornado Warning	FSD	Buena Vista, Cherokee, Clay, O'Brien	28 min
May 17, 8:48 PM CDT	Tornado Warning	FSD	Clay, Dickinson	27 min
May 17, 8:54 PM CDT	Tornado Warning	FSD	Clay, Dickinson	51 min
May 18, 5:11 PM CDT	Severe Thunderstorm Warning	FSD	Cherokee, Ida, Plymouth, Woodbury	49 min
May 18, 6:08 PM CDT	Severe Thunderstorm Warning	FSD	Plymouth, Sioux	37 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2026 Every 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.