SIOUX FALLS — Observed rainfall totals across the western Ag Belt have reached as high as 6.53 inches over the past 48 hours as of 4 p.m. CDT Sunday, with storms currently active over Iowa expected to add another 1 to 2 inches or more through the evening, keeping flooding a serious ongoing concern across the region.
Rainfall data covering September 4 through 6 shows the heaviest confirmed totals concentrated in a corridor stretching from near Pierre and Mobridge through the Sioux Falls, Yankton and Sioux City area, with a peak observed total of 6.53 inches recorded southwest of Sioux Falls. Additional heavy pockets are visible near Aberdeen, Brookings, and stretching south toward McCook and North Platte, Nebraska.
Confirmed Rainfall Totals Across the Region
- Peak observed total: 6.53 inches, southwest of Sioux Falls
- Widespread heavy totals: 3.25 to 5.75 inches common across a broad corridor from Pierre through Sioux Falls, Yankton and Sioux City
- Additional heavy pockets: Near Aberdeen, Brookings, McCook and North Platte
- Measurement window: 48-hour observed totals, September 4 to 6, 2026, through 4 p.m. CDT Sunday
- Ongoing threat: Storms currently active over Iowa, with additional totals of 1 to 2 inches or more possible through the evening
This confirmed rainfall data arrives directly on the heels of forecast guidance that had already flagged a Moderate Risk for flash flooding across the same general region, now validated by actual observed totals well into the multiple-inch range across a wide swath of South Dakota, southeastern Nebraska, and into Iowa.
Why This Rain Fell in a Pattern, Not All at Once
The radar-estimated rainfall map shows a distinctly banded pattern of heavier totals, rather than uniform rainfall spread evenly across the region. This kind of streaky, corridor-based rainfall distribution is typical when thunderstorms repeatedly track over the same general path, a training effect where each new round of storms reinforces and adds to totals in areas that were already hit by earlier rounds, while nearby communities just outside that corridor see significantly less rain.
The result is that some areas within just a few miles of each other can see dramatically different rainfall totals, with the hardest-hit corridor running roughly from central South Dakota through the Sioux Falls area and toward the Iowa-Nebraska border, while areas farther east toward Minneapolis and Rochester saw comparatively lighter totals.
Iowa Storms Add to an Already Saturated Landscape
With additional storms currently active over Iowa as of Sunday afternoon, forecasters are warning that another 1 to 2 inches or more of rain remains possible through the evening hours. Critically, this new rainfall isn’t falling on dry ground, it’s adding to a landscape that has already absorbed several inches of rain over the past two days across much of the same region, meaning the ground’s capacity to soak up additional water is likely significantly reduced…