| July 2006 | Thunderstorm Wind | Cassville | 1 killed, $1,000 | no account filed |
| August 2001 | Lightning | Bloomington | 1 killed | no account filed |
| June 2014 | Tornado (EF2) | Platteville | 5 hurt, $20,500,000 | A tornado formed along a squall line west of Platteville, just south of County Road B, and traveled through Memorial Park on to the Univ. of Wisconsin - Platteville campus. Five people were injured, one of them seriously. There was extensive damage done to five buildings and the stadium on campus. Roofs of two new residential halls were partially destroyed and a third residential hall was also damaged along with one academic building. Two large lighting structures at the football stadium were knocked over, with one crashing across the bleachers causing the concrete foundation underneath the bleachers to be substantially moved. Damage continued into nearby homes and businesses as the tornado tracked across Business Highway 151. The top level of a split level home was ripped off one house, another house lost part of a roof and a porch while several other homes had windows blown out and trees knocked down. A gas station/convenience store was leveled by the tornado where it also ripped a pump out of the ground and blew over a semi. Numerous other business and vehicles suffered blown out windows. After hitting a cemetery on the south side of town, the tornado dissipated just before reaching U.S. Highway 151 southeast of town. A total of 12 homes were destroyed with another 20 damaged.||At UW-Platteville, the tornado caused $7.3 million in damage to Bridgeway Commons, $4.8 million in damage to Rountree Commons and $1.8 million to Southwest Hall. All three buildings are dorms.||The tornado caused $1.8 million in damage to Engineering Hall, a classroom building, and $1.7 million in damage to the stadium. |
| May 1985 | Tornado (F3) | not stated | 2 hurt, $2,500,000 | no account filed |
| June 1973 | Tornado (F1) | not stated | 2 hurt, $250,000 | no account filed |
| June 1969 | Tornado (F2) | not stated | 2 hurt, $25,000 | no account filed |
| June 1998 | Tornado (F0) | Lancaster | 1 hurt, $200,000 | no account filed |
| April 2005 | Lightning | Montfort | 1 hurt | no account filed |
| June 2013 | Flash Flood | Boscobel | $7,100,000 | Very heavy rain produced flash flooding across the northeast part of Grant County. |In Boscobel, numerous houses became surrounded by water with evacuations needed, most streets were flooded and cars were under water. 650 homes were impacted by the flood waters with two dozen families displaced. County Roads M and S near Boscobel were impassable due to high water and several other county roads between Blue River and Fennimore were covered with water and impassable. Portions of County Road C southwest of Woodman were under water. The flooding washed out sections of State Highway 133 outside of Woodman and Blue River. Debris was washed down Glass Hollow and Dry Hollow Creeks where it became lodged across railroad bridges in Bagley producing flooding in the town. The railroad tracks through Woodman were washed out. Flooding debris blocked some roads around Patch Grove. 54 canoeists had to be rescued from the Wisconsin River because of rising water. |
| June 2008 | Flash Flood | Cassville | $6,500,000 | A major flash flood hit Grant County during the afternoon of June 12th impacting the communities of Lancaster, Potosi, Tennyson, Ellenboro, and other rural areas. Numerous rescues were performed from people trapped in cars, especially in the Potosi area where terrain enhanced the runoff from repeat thunderstorms. Several homes on Hippie Hollow Road in Potosi Township were destroyed along with damage to as many as 600 homes elsewhere in the region. Many highways and county roads suffered flood damage including major bridge and road infrastructure. |
| July 2007 | Flash Flood | Bagley | $2,200,000 | Flash flood waters backed up in town as debris blocked area bridges. The water was three to four feet deep in places and propane gas containers began floating on the Mississippi River. Property damage in town was extensive. |
| July 2009 | Hail | Potosi | $1,800,000 | no account filed |
| July 2009 | Thunderstorm Wind | Louisburg | $1,500,000 | no account filed |
| July 2010 | Flood | Platteville | $1,250,000 | The Grant County Emergency Manager reported that U.S. Highway 151 was closed at the SW Road interchange. County Road B was also closed for a while. County Road O sustained substantial damage and was likely closed for around a week. County Road U sustained shoulder damage. Water was also over SW Road near the intersection with Pioneer Road in the southwest part of the city of Platteville. Newspaper articles indicate at least 90 homes throughout the county were damaged by the flooding. Some of the homes had water at least 5 feet above ground level. A two day rainfall total of 9.25 inches was measured at 6 a.m. CST on July 24th in Dickeyville. A three day rainfall total of 8.96 inches in Rockville was measured at 6 a.m. CST July 24th. |
| June 2008 | Flash Flood | Patch Grove | $1,200,000 | Highways 35 and 18 were closed due to mudslides and debris. Trees were even being knocked down by the slides. |
| June 2000 | Flash Flood | Countywide | $1,200,000 | no account filed |
| July 2009 | Hail | Lancaster | $1,100,000 | Large hail was reported on Borah Ridge Road. |
| July 2017 | Flash Flood | Glenhaven | $942,000 | Locally heavy rains of 4 to 8 inches, produced flash flooding across the southern half of Grant County. Parts of State Highway 81 north of Cassville were washed out where a sinkhole formed. The flood waters around Cassville caused five people to be trapped in their residences and swept away three cars. About a dozen homes had water over the first floor and one home was a complete loss as the flood waters shifted it off the foundation. A person had to be rescued from a floating camper at a campground southeast of Cassville. Around 20 roads were closed or significantly damaged throughout the county because of the flooding. Across the county, a total of 5 homes were destroyed, 12 sustained major damage and 20 had minor damage. In Platteville, numerous streets were flooded with lots of houses surrounded by water and some basements were flooded. |
| September 2019 | Flash Flood | Bloomington | $900,000 | Runoff from heavy rains caused flash flooding to occur across the northwest portion of Grant County. Nearly every township road was closed because of flood damage across Wyalusing, Millville and Woodman townships. Roads were also closed in and near Fennimore. Water over the road, debris on the road and mudslides affected U.S. Highway 61 for about 5 miles south of Boscobel. |
| April 2008 | Flash Flood | Bagley | $800,000 | More than 20 roads were reported closed due to flash flooding. In fact, several roads remained closed, even one week after the heavy rains. There was also damage to bridges and culverts. For example, Ellenboro Road Bridge was closed for nearly a week after the heavy rains due to damage from a large amount of debris hitting the bridge. In addition, numerous farm fields were either water logged or had significant soil erosion, which could delay spring planting significantly. |
| June 2008 | Flood | Muscoda | $750,000 | Water was reported over numerous roads across the county. |
| June 2008 | Flash Flood | Muscoda | $750,000 | Numerous mudslides were reported, along with high water in valleys. |
| April 2008 | Flood | Glenhaven | $700,000 | Runoff from excessive rainfall caused significant flooding of several homes and businesses. In fact, there were approximately 70 homes which suffered damage to flood waters. Some of the locations which were hardest hit included Lancaster, Platteville, Ellenboro, Glenn Haven, Cassville and Potosi. Even a week after the heavy rains, some roads and bridges remained closed due to washouts and effects of debris hitting these structures. In addition, some farm fields remained unusable due to erosion or standing water. Grant County has been hit by major flooding in 2002, 2004, 2007 and 2008. |
| June 2014 | Tornado (EF1) | Platteville | $540,000 | A second tornado (EF1) hit the northeast corner of Platteville, near the Golf and Country Club. The track was about 1/2 mile long with a 50 yard width. Damage included some trees knocked down and a roof off an apartment building. |
| June 2002 | Flash Flood | South Portion | $500,000 | no account filed |
| July 2011 | Thunderstorm Wind | Kieler | $460,000 | High winds from severe thunderstorms created considerable damage from Keiler and Dickeyville east to Cuba City and Hazel Green. Farm buildings were damaged and corn was flattened along County Roads H and Z. Between Keiler and Cuba City, numerous homes had siding and shingles blown off or were damaged by falling trees. More than three dozen trees were blown down, a barn was destroyed and several buildings received minor damage along Banfield and Indian Creek Roads. In Dickeyville, a roof was torn off, a side wall of a building knocked down and trees were uprooted or snapped off. North of Hazel Green, a machine shed was destroyed. Numerous power lines were blown down causing power outages over a large portion of southern Grant County. |
| August 2021 | Tornado (EF3) | Boscobel | $430,000 | A NWS storm survey confirmed that an EF3 tornado occurred across northern Grant County. The tornado started in Boscobel where damage to trees, power poles and power lines occurred. The tornado then moved east/southeast before dissipating south of Blue River. Along the path, six homes sustained enough damage to be considered total losses while numerous other had minor to moderate damage. No injuries were reported. |
| September 2012 | Tornado (EF2) | Patch Grove | $420,000 | A slow moving tornado formed on the edge of a passing severe thunderstorm between Patch Grove and Bloomington. The tornado was mainly confined to one landowner near Hickory and Maine Roads in rural Grant County. Several outbuildings, a barn, and the home were demolished or heavily damaged. Trees on the property were also sheared off or blown over. Considering the roof was torn off and several walls were down or damaged, the tornado was rated an EF2 but it's possible the slow movement allowed the tornado to remain nearly stationary long enough to cause worse damage. Interviews by local residents and video evidence suggests the tornado may have moved to the northwest at times as well. |
| July 2019 | Flash Flood | Boscobel | $410,000 | Slow moving thunderstorms dropped between 3 and 5 inches of rain across the northeast portion of Grant County. Runoff from the rain caused a mudslide to occur along County Highway M south of Blue River and water covered County Highway B southeast of Ellenboro. A mudslide near Glen Haven covered some railroad tracks resulting in a train derailment. Nine cars derailed with one partially going into the Mississippi River. |
| June 2014 | Tornado (EF1) | Fennimore | $410,000 | A tornado touched down 2 miles northeast of Fennimore and skipped along an east path to 3 miles northwest of Montfort. The tornado damaged several mature hardwood trees, several outbuildings and three homes. On one farm alone, eight buildings were destroyed. The homes sustained minor damage compared to the hardwood trees and outbuildings. The tornado was rated an EF1 with maximum estimated winds of 110 mph. Total path length was 8.2 miles and the maximum width of the tornado was 600 yards. |
| June 2015 | Thunderstorm Wind | Lancaster | $400,000 | Numerous trees and power lines were blown down from Lancaster to Platteville along State Highway 133. Farm buildings were also severely damaged and homes sustained roof damage from the strong winds. |
| May 2024 | Thunderstorm Wind | Hurricane | $350,000 | Emergency management reported numerous trees and power lines down in central Grant County. |
| August 2025 | Flash Flood | Bagley | $300,000 | Emergency management reported debris blocking a railroad bridge resulting in storm water to overflow into portions of Bagley. This resulted in the inundation of several residences and prompted evacuations in the town. |
| August 2010 | Flood | Boscobel | $300,000 | Widespread rainfall amounts of 2 to 3 inches fell in two hours across much of the eastern half of Grant County. Many roads throughout the county were underwater and closed temporarily, including U.S. Highway 151 near Platteville. Damage did occur to some roads as well as to homes and businesses. The cities that had the worst impacts included Boscobel, Fennimore, Livingston, Cuba City, Kieler, and Hazel Green. |
| August 2007 | Flash Flood | Millville | $265,000 | Flash flooding affected about 40 homes across parts of mainly northern Grant County. One home was destroyed. Several bridges and roads were also damaged. |
| May 1988 | Tornado (F2) | not stated | $250,000 | no account filed |
| May 1988 | Tornado (F2) | not stated | $250,000 | no account filed |
| May 1985 | Tornado (F2) | not stated | $250,000 | no account filed |
| August 1980 | Tornado (F1) | not stated | $250,000 | no account filed |
| September 1970 | Tornado (F2) | not stated | $250,000 | no account filed |
| June 1969 | Tornado (F2) | not stated | $250,000 | no account filed |
| June 1969 | Tornado (F2) | not stated | $250,000 | no account filed |
| July 1966 | Tornado (F2) | not stated | $250,000 | no account filed |
| June 2015 | Thunderstorm Wind | Cassville | $200,000 | Trees, power lines and a barn were blown down in Cassville. A hangar at the municipal airport was damaged and a fabric covered plane that was inside the hangar was damaged extensively. Downed trees briefly blocked the Burlington Northern Santa Fe railroad tracks. Hundreds of trees were reported to have been blown down across town and several homes near the airport were damaged by the fallen trees. |
| May 1999 | Flash Flood | South Portion | $200,000 | no account filed |
| June 1998 | Thunderstorm Wind | Lancaster | $200,000 | no account filed |
| March 2020 | Tornado (EF1) | Rockville | $180,000 | An EF1 tornado touched down north of Potosi and move northeast for 6 miles before dissipating west of Ellenboro. One house, numerous farm buildings, trees and power lines were damaged along the path of the tornado. |
| April 2026 | Hail | Mt Hope | $175,000 | The public reported 2 inch diameter hail near Mount Hope. The report was relayed via social media. |
| May 2017 | Thunderstorm Wind | Lancaster | $175,000 | An estimated 70 mph wind gust occurred in Lancaster. Several barns and outbuildings were blown down and destroyed across the southwest half of Grant County as the line storms moved across. Lots of power lines were also down. |
| May 2014 | Thunderstorm Wind | Hurricane | $175,000 | Strong thunderstorms winds destroyed a 9,000 square foot metal shed dumping about 20,000 bushels of corn on the ground. The shed was destroyed but the corn was able to be salvaged. |
| June 2008 | Flood | Cassville | $175,000 | Flooding continued in many areas of southwest Wisconsin during the evening of June 12th, especially on the Platte and Grant Rivers where rises of 4 feet an hour were reported. About 50 locations on Grant County roads were closed at one point due to flood waters and damage to infrastructure. Emergency Operation Centers and shelters were opened. A state of emergency was declared for the county. |
| June 2017 | Thunderstorm Wind | Livingston | $170,000 | More than 20 power poles were snapped causing power lines to go down along State Highway 80 between Livingston and Montfort. Farm buildings were damaged north of Livingston. |
| May 2004 | Flash Flood | Countywide | $150,000 | no account filed |
| June 2004 | Flash Flood | Southwest Portion | $150,000 | no account filed |
| June 1998 | Thunderstorm Wind | Lancaster | $150,000 | no account filed |
| June 2015 | Thunderstorm Wind | Hazel Green | $110,000 | An estimated wind gust of 65 mph blew down trees and powerlines in and around Hazel Green. The winds also damaged farm buildings and homes. |
| May 2024 | Hail | Dickeyville | $100,000 | Golf ball sized hail was reported near Dickeyville by local law enforcement. |
| August 2005 | Tornado (F1) | Muscoda | $100,000 | no account filed |
| May 2004 | Flash Flood | North Portion | $100,000 | no account filed |
| June 1998 | Thunderstorm Wind | Bagley | $95,000 | Jellystone Campground was hit with many campers damaged. |
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