A wet August resulted in renewed minor to locally moderate river flooding along portions of the middle Big Sioux River.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS FSD wrote it up.
A wet August resulted in renewed minor to locally moderate river flooding along portions of the middle Big Sioux River.
The local office's own words before the first event, 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 the first event at Aug 16, 9:18 PM CST, 4 hours 42 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD 1018 PM CDT Sat Aug 16 2025 .KEY MESSAGES... - A few stronger storms could return overnight mainly across the Highway-14 corridor and portions of southwestern MN. The main threats would be Ping-Pong Ball sized hail and damaging winds up to 65 mph. - Next chances for organized convection likely come on Sunday and Monday with a heavy rainfall threat. However, some details still remain uncertain at this time. - Much quieter conditions likely return for much of the week bringing in lower dew points, near-normal temperatures, and limited precipitation chances.&& .DISCUSSION... Issued at 228 PM CDT Sat Aug 16 2025 CURRENTS & TONIGHT: Another warm and humid day continues! Taking a look across the area, areas of stratus with pockets of sprinkles to light shower continue to develop mainly along a Bonesteel to Sioux Falls to Slayton, MN line this afternoon. With this being fueled by lingering convergence along a warm front draped along I-90 corridor and a weakening LLJ, not expecting this activity to last past the early afternoon before dissipating. Otherwise, the focus continues to be on the muggy conditions. As of 18z, dew points have reached the mid to upper 70s across most of the area with temperatures varying between the low to mid 80s. Given the set up, we're still on track for many areas south of I-90 to see heat index values in the 95 to 105 degree range through this evening. However, the combination of this morning's rainfall and lingering stratus will likely keep things more isolated vs widespread than originally expected. Nonetheless, our heat advisory remains in effect through 8 pm. Looking aloft, a true "Rex Blocking" pattern continues with our area locked into southwesterly to westerly flow. As the previously mentioned warm front continues to lift northwards towards the highway-14 corridor throughout the evening and intersects an approaching shortwave overnight, should see scattered showers and thunderstorms develop just to the north of the near-surface feature. While most of our area should stay clear of this developing activity, can't complete rule out some of these showers and thunderstorms moving across portions of the Highway-14 corridor and southwestern MN between 09z-13z (4am to 8am). With this in mind, an isolated large hail risk will be possible through daybreak on Sunday with stronger storms being capable of producing up to Ping-Pong Ball sized (1.5") given the lapse rates around 6.5-7 deg C/km and lingering instability (1000-1500 J/kg). Can't also rule out a few isolated gusts up to 65 mph given DCAPE values between 1000-1200 J/kg. Lastly, should see overnight temperatures gradually decrease into the upper 60s to low 70s. SUNDAY & MONDAY: Looking into Sunday, an active pattern continues aloft as a mid-level wave lifts across the northern plains. While the bulk of the activity will likely continue near the warm front closer to central MN and the ND/SD border, increasing lift and dPVA in association with an approaching cold front should triggering scattered showers and thunderstorms from the early afternoon to evening hours. Given a decently unstable environment characterized by 1500-2500 J/kg of instability and 20-30 kts of shear, an isolated to scattered severe risk will be possible along and ahead of the front with half dollar sized hail (1.25") and damaging winds up to 65 mph being the primary risks. While the better severe risk will likely occur between 1 pm to 8 pm, could see additional shower and thunderstorm chances develop into the overnight hours as a nocturnal LLJ (30-40 kt) strengthens across areas east of I-29. By Monday, quasi-zonal flow returns aloft along with quieter conditions for most of the day. Temperatures will begin to trend cooler as northerly to northwesterly surface winds and lingering cold air advection (CAA) leads to highs in the low 80s to low 90s with the coolest conditions north of I-90. Shower and thunderstorm chances (20%-30%) will once again increase overnight as another weak wave moves through areas west of the James River Valley. While there could be another isolated severe risk with this system, there is still some lingering uncertainty as far as evolution and timing of this developing activity. TUESDAY ONWARDS: Heading into the extended period, much quieter conditions should return by Tuesday as surface ridging begins to stretch down from the Great Lakes Region. With an influx of CAA aloft and light easterly to southeasterly surface winds, expect temperatures to trend towards our seasonal normals with highs mainly in the low to upper 80s. By Thursday, could see a slight boost in temperatures as increasing WAA ahead of a cold front leads to highs in the 80s and 90s with the warmest conditions west of the James River Valley. Our next rain chances likely come between Thursday night and Friday morning with the cold front. However, the finer details remain uncertain at this time. Lastly, long-range guidance continues to keep temperatures around our season ranges headed into the weekend so expect highs in the 80s. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1014 PM CDT Sat Aug 16 2025 MVFR ceilings look to be a little more stubborn across areas mainly north of I-90 through the overnight hours. Some patchy MVFR ceilings may linger through the morning as well. Attention turns to thunderstorm potential with a few strong storms possible in southwest MN and west along highway 14 through the early overnight hours. Much of this activity is expected to shift north of highway 14. The a stronger wave moves into the area on Sunday with periodic chances for thunderstorms through the late morning into Sunday evening. Some of these storms could be severe with heavy rainfall. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...05 AVIATION...08
Hazardous Weather Outlook National Weather Service Sioux Falls SD 325 PM CDT Sat Aug 16 2025 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-172030- 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- 325 PM CDT Sat Aug 16 2025 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. Heat index values between 95 and 105 degrees are expected this afternoon with the highest values south of I-90. Isolated to scattered thunderstorms may develop again tonight, mainly through the Highway 14 corridor and portions of southwestern Minnesota. A few of these storms could be severe with hail to the size of ping- pong balls and wind gusts to 65 mph. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Isolated to scattered thunderstorm risks again Sunday afternoon and evening. Greatest severe risk is 1pm to 8pm with hail to the size of half dollars and damaging wind gusts up to 65 mph. A few storms are again possible Monday evening. Details remain uncertain but storms may be capable of producing large hail and damaging wind gusts. Please continue to monitor for forecast and thunderstorm risk changes. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
953 PM CDT Sat Aug 16 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0405 AM Tstm Wnd Dmg Edgerton 43.87N 96.13W
08/16/2025 Pipestone MN Public
Social media report of 3 inch plus branches
down. Time estimated by radar.
&&
AJPThe national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
The Big Sioux River near Estelline rose above flood stage on the morning of August 17th, cresting around 2.53 feet above flood stage (1646.53 ft) on August 19th. This crest is in the moderate flood category. The river then fell below flood stage on the morning of August 28th.
The Big Sioux River near Bruce rose above flood stage on the evening of August 18th, cresting around 2.22 feet above flood stage (10.22 ft) on August 20th. This crest is in the moderate flood category. The river remained above flood stage into September.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2025Every state in 2025This day in weather historyWarnings in South Dakota, August 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-30. Each event’s entry at NCEI: 1282766, 1282767.