| April 2017 | Flash Flood | Alton | $4,000,000 | Numerous county roads and bridges were damaged by flash floods. Several campgrounds and river access areas were severely damaged across the county. This report will contain the total dollar estimate for flood damage to infrastructure, businesses, and homes across Oregon County. $3M in damages were reported to roads alone in the county. |
| April 2025 | Flash Flood | Alton | $20,000 | Several city streets were flooded causing vehicles to become stranded. |
| May 2017 | Thunderstorm Wind | Alton | $10,000 | A large tree fell on to a truck in Alton. This report was from social media. |
| July 2015 | Thunderstorm Wind | Alton | $10,000 | Several power lines and trees were blown down. Several main roads were blocked by trees and power lines down. |
| June 2014 | Hail | Alton | $10,000 | no account filed |
| June 2002 | Thunderstorm Wind | Alton | $10,000 | no account filed |
| February 2001 | Thunderstorm Wind | Alton | $10,000 | no account filed |
| April 1999 | Thunderstorm Wind | Alton | $6,000 | no account filed |
| September 2012 | Thunderstorm Wind | Alton | $5,000 | A mobile home was blown off its foundation. |
| April 2009 | Thunderstorm Wind | Alton | $5,000 | Thunderstorm wind gusts damaged the roof of a church and knocked over a few trees. |
| June 2009 | Thunderstorm Wind | Alton | $5,000 | Severe thunderstorm wind gusts knocked over a large tree and landed on a car. |
| August 2006 | Thunderstorm Wind | Alton | $5,000 | Thunderstorm wind gusts downed a few power lines. |
| June 1994 | Hail | Alton | $5,000 | Reported by the county sheriff and Missouri Highway Patrol (Troop G). A local newspaper also reported numerous power poles and trees snapped off with approximately 3,000 people without power across the county. |
| June 1994 | Thunderstorm Wind | Alton | $5,000 | Reported by the county sheriff and Missouri Highway Patrol (Troop G). A local newspaper also reported numerous power poles and trees snapped off with approximately 3,000 people without power across the county. |
| March 2026 | Thunderstorm Wind | Alton | $2,000 | Thunderstorm winds downed two trees in Alton. |
| January 2008 | Tornado (EF0) | Alton | $1,000 | A National Weather Service storm survey revealed that a weak EF-0 tornado damaged a few outbuildings south of Alton. A motorcycle shop sustained the most damage as a barn that sheltered several new motorcycles was destroyed. |
| April 1999 | Thunderstorm Wind | Alton | $1,000 | no account filed |
| June 1994 | Hail | Alton | $500 | Reported by the county sheriff and Missouri Highway Patrol (Troop G). A local newspaper also reported numerous power poles and trees snapped off with approximately 3,000 people without power across the county. |
| April 1994 | Hail | Alton | $500 | no account filed |
| April 2025 | Flash Flood | Alton | - | The Piney Creek at Highways 160 and 19 flooded several structures. |
| April 2025 | Flash Flood | Alton | - | Several city streets were flooded with a few structures reporting water coming into the building. |
| April 2025 | Flash Flood | Alton | - | Excessive rainfall caused high water to occur around town which caused flooding in the Harps Store. |
| April 2025 | Flash Flood | Alton | - | The Piney Creek at Highways 160 and 19 flooded several structures. |
| April 2025 | Flash Flood | Alton | - | Tucker Creek was flowing out of its banks into fields and some roads. |
| April 2025 | Hail | Alton | - | Hen egg sized hail was reported in a mainly rural portion northeast of Alton, Mo. |
| August 2022 | Thunderstorm Wind | Alton | - | Several trees were reported down causing power outages on Old Cane Bluff Road near Highway 19. |
| November 2022 | Thunderstorm Wind | Alton | - | Multiple trees and large limbs were reported down. |
| April 2020 | Hail | Alton | - | Half dollar sized hail was reported. |
| May 2017 | Thunderstorm Wind | Alton | - | Numerous trees were blown down around Alton and Winona. |
| August 2016 | Flash Flood | Alton | - | Several low water crossings were flooded across the county. |
| July 2015 | Flood | Alton | - | Highway P west of Alton was flooded and impassable. |
| December 2015 | Thunderstorm Wind | Alton | - | A large tree was blown down in the town of Alton. |
| July 2012 | Thunderstorm Wind | Alton | - | A tree was blown down. |
| May 2007 | Flash Flood | Alton | - | Heavy rain caused flooding over several low water crossings east of Alton. |
| April 2006 | Tornado (F0) | Alton | - | A small tornado tracked eight miles across rural central Oregon County. Only damage that occurred from this feature was minor damage to trees. |
| May 2006 | Tornado (F0) | Alton | - | A National Weather Service storm survey revealed that a weak tornado tracked through a highly remote and wooded area of eastern Oregon County. The tornado initially touched down three miles east of Riverton near County Road 152 just north of Highway 160, and moved two miles east. Intermitten minor tree damage was found along the 20 yard wide path. |
| May 2006 | Flash Flood | Alton | - | Several low water crossings near the community of Alton became inundated with flash flooding from heavy thunderstorms. |
| September 2006 | Thunderstorm Wind | Alton | - | Thunderstorm wind gusts downed trees in Alton. |
| September 2006 | Flash Flood | Alton | - | Flooding was reported over several county roads. |
| September 2006 | Thunderstorm Wind | Alton | - | Thunderstorm wind gusts downed trees in the Alton area. |
| June 2005 | Thunderstorm Wind | Alton | - | A line of severe thunderstorms downed numerous trees across the county. |
| June 2005 | Thunderstorm Wind | Alton | - | Several trees were downed from east of Alton northward to along the Shannon and Oregon county line from severe thunderstorm wind gusts. |
| August 2005 | Thunderstorm Wind | Alton | - | Downburst winds downed several trees in a wooded area east of Alton. |
| July 2004 | Thunderstorm Wind | Alton | - | Severe thunderstorm wind gusts downed a few trees along Highway 160 west of Alton. |
| July 1997 | Thunderstorm Wind | Alton | - | Thunderstorm winds downed trees along Highway P. |
| July 2015 | Hail | Alton | - | no account filed |
| July 2015 | Hail | Alton | - | no account filed |
| October 2014 | Hail | Alton | - | no account filed |
| October 2014 | Hail | Alton | - | no account filed |
| April 2011 | Hail | Alton | - | no account filed |
| May 2011 | Hail | Alton | - | no account filed |
| June 2011 | Hail | Alton | - | no account filed |
| July 2009 | Hail | Alton | - | no account filed |
| November 2007 | Hail | Alton | - | no account filed |
| April 2006 | Hail | Alton | - | no account filed |
| April 2006 | Hail | Alton | - | no account filed |
| April 2006 | Hail | Alton | - | no account filed |
| April 2006 | Hail | Alton | - | no account filed |
| May 2006 | Hail | Alton | - | no account filed |
| May 2003 | Hail | Alton | - | no account filed |