| May 2007 | Flood | Riverton | $500,000 | Heavy rainfall over the weekend of May 4th through the 6th, caused the Nishnabotna River to flood across Fremont county. The Nishnabotna River at Hamburg reached a prolonged crest of around 32.4 feet between 715 pm and 1145 pm on May 8th. Flood stage is 23 feet. The river at Hamburg first crossed flood stage around 6 am CDT on May 6th and didn't drop below flood stage until around 7 am on May 15th.|The flooding closed Interstate 29 for a while and an agricultural levee broke south of town sending significant amounts of water across agricultural bottom lands and county roads in the region early May 7th.|Flooding was also observed along the East Nishnabotna River northeast of Riverton to it's merger with the West Nishnabotna near Riverton where it forms the Nishnabotna that passes near Hamburg. Some home damage and county roads closures were reported in the area due to flood waters. |
| December 2015 | Flood | Riverton | $25,000 | Heavy rainfall during mid December led to river flooding along both the East and West Nishnabotna Rivers. The West Nishnabotna River crested during the late afternoon on the 14th, while the East Nishnabotna crested late on the 15th. The river flooding was generally confined to low agricultural land along the rivers, but State Highway J46 was closed due to flooding. |
| October 2014 | Flood | Riverton | $5,000 | Heavy rainfall in late September led to river flooding into early October along the West Nishnabotna River. The river rose to flood stage in the afternoon on the 1st, crested in the early morning on the 2nd, and fell below flood stage later that evening. The flooding was minor and confined to low-lying areas along the river. |
| September 2014 | Flood | Riverton | $5,000 | A slow moving thunderstorm complex lead to heavy rainfall on the 9th causing the East Nishnabotna River to rise above flood stage around the Riverton area. The river rose above flood stage during the afternoon on the 10th, crested during the morning on the 11th, and fell below flood stage later that afternoon. The flooding was minor and confined to low-lying areas. |
| August 2014 | Flood | Riverton | $5,000 | Repeated thunderstorms on the 27th and 28th of August caused heavy rainfall and the West Nishnabotna River to go into flood. The river rose above flood stage on the afternoon of the 28th, crested that late evening, and fell below flood stage in the early morning on the 29th. The flooding was generally minor and confined to low-lying areas along the river. |
| September 2014 | Flood | Riverton | $5,000 | Heavy rainfall at the end of August allowed the West Nishnabotna River to rise above flood stage on the early morning on the 2st, crest during the late morning, and fall below flood stage during the afternoon. The flooding was minor and confined to low-lying areas along the river. |
| June 2014 | Flood | Riverton | $2,000 | Heavy rain caused the Nishnabotna River to flood around the Hamburg area on June 4th. The river near Hamburg crested a little over 26.5 feet during the mid afternoon of June 4, flood stage is 25 feet. The flooding mainly impacted farmland along the river. |
| May 1995 | Thunderstorm Wind | Riverton | $1,000 | no account filed |
| April 2026 | Tornado (EFU) | Riverton | - | Video and photo evidence of a small tornado near this location. |
| April 2026 | Tornado (EF0) | Riverton | - | Several videos and photographs from multiple angles indicated that a weak tornado developed and moved to the east northeast along this approximate path. While the near-surface dust cloud was wider, the core circulation was quite narrow and weak. The only damage along the track was minor tree damage as it crossed mostly open fields. Maximum wind speeds were estimated at 70 mph. |
| August 2025 | Thunderstorm Wind | Riverton | - | A swath of damaging winds moved through Fremont County, Iowa, during the morning of August 10th, 2025. The event produced widespread damage, primarily characterized by high-end estimated straight-line wind gusts between 90 and 95 miles per hour across the county, confirmed by emergency management. ||The most significant damage occurred near Farragut and Riverton. Wind gusts estimated at 95 miles per hour 3 miles south-southeast of Farragut caused significant roof and wall damage to a large barn and completely destroyed a shed. Additionally, winds estimated at 90 miles per hour were responsible for extensive tree damage in both the towns of Riverton and Farragut. |
| April 2024 | Hail | Riverton | - | The office received a public report of quarter sized hail. |
| May 2016 | Flood | Riverton | - | Ther river crested at 23.52 feet, which flooded County Road J-46 near the river. |
| May 2016 | Flood | Riverton | - | Lowland flooding along both banks of the river was observed with the river cresting at 23.61 feet. |
| May 2016 | Flood | Riverton | - | Flooding is observed throughout the floodplain on both side of the river, and County Road J-46 is also flooded. |
| May 2016 | Flood | Riverton | - | Minor lowland flooding was observed along the river. |
| June 2015 | Flood | Riverton | - | Minor flooding was observed along the main stem of the Nishnabotna River near Hamburg. The flooding was confined to agricultural low lands within the levee. |
| July 2014 | Flood | Riverton | - | Local law enforcement reported that the intersection of 250th and J64 was closed due to high water. |
| February 2011 | Flood | Riverton | - | Ice jam flooding was observed along the East Nishnabotna River which crossed County Road J46 near Riverton. Damage was apparently minimal. |
| April 2008 | Hail | Riverton | - | The hail was accompanied by winds strong enough to blow down a few branches. |
| June 2008 | Flood | Riverton | - | A week of heavy rain producing thunderstorms through June 11th fell across the Nishnabotna River basin in southwest Iowa. The heavy rain caused flooding along the East Nishnabotna from around Elliott downstream through the Red Oak area and then into Fremont county where it merges with the West Nishnabotna River near Hamburg. The river at Red Oak reached a 24 foot crest around 415am CDT on June 13th, flood stage is 18 feet. The river at Red Oak fell below flood stage in the mid afternoon hours of June 13th. The flooding closed a four-mile stretch of Highway 275 near Hamburg from the Missouri state line north, and also closed several county roads, especially around Riverton. Agricultural lowlands in the area were also flooded. |
| October 2007 | Flood | Riverton | - | Heavy rain produced a period of flooding along the mainstem Nishnabotna River from the merger of the east and west branches downstream to its merger with the Missouri River south of Hamburg. The river at Hamburg crested at 25.1 feet around 1030 pm CDT on October 16th, flood stage is 23 feet. The river at Hamburg was above flood stage from around 530 am CDT on the 15th until 9 am on the 18th. |
| June 2005 | Thunderstorm Wind | Riverton | - | Thunderstorm wind gusts estimated at 60 to 70 mph knocked down large tree limbs along Highway SR-2. |
| June 2005 | Thunderstorm Wind | Riverton | - | Thunderstorm wind gusts estimated at 60 mph knocked down large tree branches in town. |
| August 2004 | Tornado (F2) | Riverton | - | A tornado that eventually reached f2 in strength first touched down 2.5 miles southwest of Riverton. The tornado reached it's maximum intensity and maximum damage width of 1/2 mile when it destroyed a home on 270th street. The tornado also caused signifcant damage to another house, several vehicles, other farm outbuildings, crops and trees before lifting 1 mile southeast of Riverton. |
| March 2002 | Hail | Riverton | - | Hail between dime and quarter size was reported by law enforcement personel in Riverton. |
| June 2017 | Hail | Riverton | - | no account filed |
| March 2016 | Hail | Riverton | - | no account filed |
| May 2013 | Hail | Riverton | - | no account filed |
| June 2008 | Hail | Riverton | - | no account filed |
| June 2008 | Hail | Riverton | - | no account filed |
| March 2006 | Hail | Riverton | - | no account filed |
| May 2006 | Hail | Riverton | - | no account filed |
| June 2005 | Hail | Riverton | - | no account filed |
| June 2005 | Hail | Riverton | - | no account filed |
| May 2004 | Hail | Riverton | - | no account filed |
| May 2003 | Hail | Riverton | - | no account filed |
| May 1998 | Hail | Riverton | - | no account filed |
| May 1996 | Hail | Riverton | - | no account filed |
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