A complex of storms moved across northeast Iowa during the late afternoon and evening of August 27th. These storms produced two tornadoes in the vicinity of Marble Rock (Floyd County). The first tornado was an EF0 west of Marble Rock that only caused some minor crop and structural damage to a farm. The second tornado was rated as an EF1 that passed just to the south of Marble Rock as it moved southeast. Nearly all the buildings on one farm were destroyed and several other farm buildings and homes sustained some damage. The storms also produced heavy rain with totals ranging from 3 to 8 inches. Flash flooding from this rain closed several roads, including U.S. Highway 18 near New Hampton (Chickasaw County) and some homes sustained water damage. A train derailment southwest of New Hampton resulted from flooding along the Wapsipinicon River prompted officials to evacuate nearby residents when a tank car leaked anhydrous ammonia. The Chickasaw County Sheriff issued a no travel advisory for parts of the county because of the flooding. The Governor of Iowa issued a disaster proclamation for Allamakee, Chickasaw, Clayton, Floyd, Howard, Mitchell and Winneshiek Counties. A previous disaster proclamation was still in effect for Fayette County.

Tornado in FLOYD, IOWA
From 27-AUG-21 16:57:00 to 27-AUG-21 17:11:00 (CST-6)
Location: AUREOLA
Tornado F-scale: EF1
Property damage: 280.00K
Crop damage: 40.00K
Reported by: NWS Storm Survey

An EF1 tornado developed just to the west of Marble Rock and passed south of town as it traveled southeast. Several farms sustained damage along the track with one farm having nearly every outbuilding destroyed and several large propane tanks were knocked over.

Tornado in FLOYD, IOWA
From 27-AUG-21 16:51:00 to 27-AUG-21 16:54:00 (CST-6)
Location: KNOOP ARPT
Tornado F-scale: EF0
Property damage: 10.00K
Crop damage: 10.00K
Reported by: NWS Storm Survey

An EF0 tornado formed west of Marble Rock and move to the east before dissipating. Damage was primarily limited to crops but one farm did sustain some damage to outbuildings.

Thunderstorm Wind in WINNESHIEK, IOWA
From 27-AUG-21 18:00:00 to 27-AUG-21 18:00:00 (CST-6)
Location: FT ATKINSON
Magnitude: 40.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Power lines were blown down in Fort Atkinson.

Thunderstorm Wind in WINNESHIEK, IOWA
From 27-AUG-21 17:58:00 to 27-AUG-21 17:58:00 (CST-6)
Location: CALMAR
Magnitude: 45.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Power lines were blown down in Calmar.

Flood in FLOYD, IOWA
From 28-AUG-21 10:44:00 to 30-AUG-21 07:45:00 (CST-6)
Location: CHARLES CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Runoff from heavy rains pushed the Cedar River out of its banks in Charles City. The river crested over four feet above the flood stage at 16.27 feet on the 29th.

Flood in WINNESHIEK, IOWA
From 27-AUG-21 21:59:00 to 29-AUG-21 18:46:00 (CST-6)
Location: SPILLVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Runoff from heavy rains pushed the Turkey River out of its banks in Spillville. The river crested over six feet above the flood stage at 15.1 feet on the 28th.

Thunderstorm Wind in WINNESHIEK, IOWA
From 27-AUG-21 18:19:00 to 27-AUG-21 18:19:00 (CST-6)
Location: OSSIAN
Magnitude: 40.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Power lines were blown down in Ossian.

Thunderstorm Wind in CLAYTON, IOWA
From 27-AUG-21 19:01:00 to 27-AUG-21 19:01:00 (CST-6)
Location: MONONA
Magnitude: 45.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Power lines were blown down in Monona.

Flood in CLAYTON, IOWA
From 28-AUG-21 09:05:00 to 31-AUG-21 04:45:00 (CST-6)
Location: ELKADER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Runoff from heavy rains pushed the Turkey River out of its banks in Elkader. The river crested almost eleven feet above the flood stage at 22.82 feet on the 30th. This was the fourth highest crest on record.

Flood in CLAYTON, IOWA
From 28-AUG-21 17:44:00 to 31-AUG-21 05:36:00 (CST-6)
Location: GARBER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Runoff from heavy rains pushed the Turkey River out of its banks in Garber. The river crested over six feet above the flood stage at 23.39 feet. This was the fourth highest crest on record.

Flash Flood in MITCHELL, IOWA
From 27-AUG-21 22:32:00 to 28-AUG-21 04:15:00 (CST-6)
Location: OTRANTO
Flood cause: Heavy Rain
Property damage: 750.00K
Crop damage: 2.70M
Reported by: Department of Highways

Runoff from heavy rains pushed the Little Cedar River out of its banks. County roads A46 and T64 near New Haven had to be closed because of the flood waters. Spring Creek also went out if its banks causing U.S. Highway 18 to be closed near Osage. A dam on the Cedar River near Mitchell sustained damage from the flood waters. Numerous gravel roads across the county suffered washouts.

Flash Flood in FAYETTE, IOWA
From 28-AUG-21 00:30:00 to 28-AUG-21 04:15:00 (CST-6)
Location: ALPHA
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 3.20M
Reported by: Law Enforcement

Runoff from heavy rain caused several streams to out of their banks across Fayette County. Flood waters from the Little Turkey River caused officials to evacuate campers from Gouldsburg County Park and close roads around Waucoma.

Flash Flood in FLOYD, IOWA
From 27-AUG-21 23:30:00 to 28-AUG-21 04:15:00 (CST-6)
Location: FLOYD HANRY ARPT
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 500.00K
Reported by: Broadcast Media

Runoff from heavy rains caused some flash flooding to occur across the eastern sections of Floyd County. Some gravel roads were washed out and some chickens were washed away from a farm.

Tornado in FLOYD, IOWA
From 27-AUG-21 16:50:00 to 27-AUG-21 16:51:00 (CST-6)
Location: KNOOP ARPT
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 2.00K
Reported by: NWS Storm Survey

This very brief track was found in Sentinel satellite imagery and stayed in fields for its existence. Based on the location in the supercell, inflow wind trajectories along the left side of the track, and striation patterns in the fields, there is a high likelihood that this was an anti-cyclonic tornado.

Flash Flood in CHICKASAW, IOWA
From 28-AUG-21 00:37:00 to 28-AUG-21 04:15:00 (CST-6)
Location: DEERFIELD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Runoff from heavy rains caused numerous streams to go out of their banks across Chickasaw County. Roads throughout the township of New Hampton were had to be closed because of flood waters.

Heavy Rain in MITCHELL, IOWA
From 27-AUG-21 12:34:00 to 27-AUG-21 22:22:00 (CST-6)
Location: ST ANSGAR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

In St. Ansgar, 9.73 inches of rain fell.

Flood in CHICKASAW, IOWA
From 28-AUG-21 04:15:00 to 28-AUG-21 20:15:00 (CST-6)
Location: DEERFIELD
Flood cause: Heavy Rain
Property damage: 500.00K
Crop damage: 2.50M
Reported by: Department of Highways

Numerous roads were closed across Chickasaw County because of flood waters in the Ionia area. The East Fork of the Wapsipinicon River went out of its banks forcing officials to close U.S. Highway 18 near Fredericksburg. A train attempting to cross the Wapsipinicon River southwest of New Hampton derailed causing officials to evacuate nearby residents when one of the tank cars leaked some anhydrous ammonia.

Heavy Rain in FAYETTE, IOWA
From 27-AUG-21 18:02:00 to 28-AUG-21 02:44:00 (CST-6)
Location: ELDORADO
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Near Eldorado, 4.9 inches of rain fell.

Flood in FAYETTE, IOWA
From 28-AUG-21 04:15:00 to 28-AUG-21 16:15:00 (CST-6)
Location: WAUCOMA
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flood waters from the Little Turkey River prompted officials to evacuate half of Waucoma. The flood waters caused minor damage to some buildings.

Thunderstorm Wind in CHICKASAW, IOWA
From 27-AUG-21 17:32:00 to 27-AUG-21 17:32:00 (CST-6)
Location: NASHUA
Magnitude: 45.00 EG
Property damage: 3.00K
Crop damage: 3.00K
Reported by: Public

Telephone poles and crops were damaged by winds southeast of Nashua.

Funnel Cloud in CHICKASAW, IOWA
From 27-AUG-21 17:37:00 to 27-AUG-21 17:37:00 (CST-6)
Location: REPUBLIC
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A funnel cloud was sighted southeast of Ionia.

Flood in MITCHELL, IOWA
From 28-AUG-21 04:15:00 to 28-AUG-21 20:15:00 (CST-6)
Location: RICEVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

A road east of New Haven had to be closed due to flood waters from Watsons Creek.

Flood in FLOYD, IOWA
From 28-AUG-21 04:15:00 to 28-AUG-21 20:15:00 (CST-6)
Location: COLWELL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

A road was closed south of Colwell due to flood waters from the Cedar River.

Lightning in CHICKASAW, IOWA
From 27-AUG-21 17:48:00 to 27-AUG-21 17:48:00 (CST-6)
Location: IONIA
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Lightning struck a home in Ionia.

Thunderstorm Wind in ALLAMAKEE, IOWA
From 27-AUG-21 18:35:00 to 27-AUG-21 18:35:00 (CST-6)
Location: POSTVILLE
Magnitude: 50.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Power lines were blown down in Postville.

Flood in WINNESHIEK, IOWA
From 28-AUG-21 04:15:00 to 28-AUG-21 20:15:00 (CST-6)
Location: HAUGENDALE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

Roads were closed in the vicinity of Spillville and Ridgeway due to flood waters from the Turkey River and Walnut Creek.

Heavy Rain in MITCHELL, IOWA
From 27-AUG-21 13:24:00 to 27-AUG-21 22:24:00 (CST-6)
Location: NEW HAVEN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

East of Osage, 8.07 inches of rain fell.

Heavy Rain in CHICKASAW, IOWA
From 27-AUG-21 10:40:00 to 28-AUG-21 01:46:00 (CST-6)
Location: NEW HAMPTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

In New Hampton, 8.5 inches of rain fell.

Heavy Rain in CHICKASAW, IOWA
From 27-AUG-21 10:02:00 to 28-AUG-21 00:46:00 (CST-6)
Location: CHICKASAW
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

West of Ionia, 6.95 inches of rain fell.