A nearly stationary west to east frontal boundary was located across Nebraska and Iowa for several days. With an extremely moist atmosphere featuring near record precipitable water in place, several weak disturbances resulted in prolific rainfall from 3 to as much as 10 inches.

Flood in LYON, IOWA
From 20-SEP-18 09:00:00 to 26-SEP-18 08:00:00 (CST-6)
Location: GRANITE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls metro area from September 18-20 totaled generally 5 to 7 inches. Moderate flooding resulted with significant flooding of crop and pasture land as the Big Sioux River at Brandon (gage site BBSS2) crested 3.3 feet above flood stage on September 21.

Flood in LYON, IOWA
From 20-SEP-18 11:00:00 to 25-SEP-18 15:00:00 (CST-6)
Location: KLONDIKE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls area and southward in the Big Sioux basin from September 18-20 totaled generally 5 to 7 inches. Major flooding resulted with all crop and pasture land in the half-mile wide flood plain inundated. The Big Sioux River above Canton (gage site CBSS2) crested 6.0 feet above flood stage on September 22, the third highest crest on record.

Flood in SIOUX, IOWA
From 20-SEP-18 13:00:00 to 26-SEP-18 08:00:00 (CST-6)
Location: FAIRVIEW
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls area and southward in the Big Sioux basin from September 18-20 totaled generally 5 to 7 inches. Moderate flooding resulted with all crop and pasture land in the half-mile wide flood plain inundated as the Big Sioux River at Fairview (gage site FVWS2) crested 6.7 feet above flood stage on September 22.

Flood in SIOUX, IOWA
From 20-SEP-18 11:00:00 to 25-SEP-18 15:00:00 (CST-6)
Location: CHATSWORTH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls area and southward in the Big Sioux basin from September 18-20 totaled generally 5 to 7 inches. Major flooding resulted with all crop and pasture land in the half-mile wide flood plain inundated. The Big Sioux River above Canton (gage site CBSS2) crested 6.0 feet above flood stage on September 22, the third highest crest on record.

Flood in SIOUX, IOWA
From 20-SEP-18 03:00:00 to 30-SEP-18 03:00:00 (CST-6)
Location: LEBANON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Widespread upstream rainfall in the Big Sioux basin from September 18-20 totaled generally 5 to 10 inches, resulting in major flooding. South Dakota Highway 46 was closed, with several farm houses isolated by high water as the Big Sioux River above Hawarden (gage site HWDI4) crested 11.1 feet above flood stage on September 22.

Flood in PLYMOUTH, IOWA
From 20-SEP-18 18:00:00 to 30-SEP-18 23:59:00 (CST-6)
Location: AKRON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Widespread upstream rainfall in the Big Sioux basin from September 18-20 totaled generally 5 to 10 inches, resulting in major flooding. South Dakota Highway 48 near the intersection of Iowa Highway 12 along with several farm houses were inundated by high water as the Big Sioux River at Akron (gage site AKRI4) crested 6.2 feet above flood stage on September 23. Highway 48 was reopened on September 27, but the river remained in minor flood stage at the end of the month.

Flood in PLYMOUTH, IOWA
From 21-SEP-18 00:00:00 to 30-SEP-18 23:59:00 (CST-6)
Location: WESTFIELD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Widespread upstream rainfall in the Big Sioux basin from September 18-20 totaled generally 5 to 10 inches, resulting in major flooding. A few farm buildings were flooded with widespread crop and pasture land flooding as the Big Sioux River near Richland (gage site BSRS2) crested 6.2 feet above flood stage on September 23. The river remained in minor flood stage at the end of the month.

Flood in PLYMOUTH, IOWA
From 23-SEP-18 12:00:00 to 27-SEP-18 18:00:00 (CST-6)
Location: MILLNERVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Widespread upstream rainfall in the Big Sioux basin from September 18-20 totaled generally 5 to 10 inches, with downstream routing resulting in minor flooding. Significant flooding of crop and pasture land occured as the Big Sioux River near Jefferson (gage site BSJS2) crested 4.8 feet above flood stage on September 25.