| August 1998 | Flash Flood | Brookfield | 2 killed, 1 hurt, $17,300,000 | no account filed |
| April 1984 | Tornado (F4) | not stated | 1 killed, 14 hurt, $2,500,000 | no account filed |
| June 2008 | Flash Flood | Wales | 1 killed, $25,000 | Heavy rains led to flash flooding that generated water levels of 2 to 4 feet deep on many low-lying roads, especially near existing lakes. Several vehicles stalled in the deep water and were damaged. A 68-year-old man left a tavern around 2245 CST and drove into a flooded area. He attempted to walk/swim away from his vehicle and drowned. |
| April 2026 | Lightning | Waukesha Co Arpt | 1 killed | Report of a lightning-related fatality in a gas station parking lot. |
| June 2010 | Tornado (EF2) | Eagle | 15 hurt, $20,600,000 | An EF2 tornado developed about 1.9 miles west-southwest of the Village of Eagle, roughly 1/2 mile south-southeast of the intersection of STH 59 and CTH S, just west of CTH S and west of a horse-riding ranch, and moved east-northeast through the Eagle and then moved due east and then east-southeast before dissipating about 1.94 miles southeast of Jericho, just within Mukwonago County Park, 1000 feet east of Genevieve Drive. Fifteen people sustained minor injuries. One hundred thirty-four homes received minor damage, 67 homes had major damage, and 8 homes were destroyed, mainly in the southern part of the village. Another 75 homes were minimally affected. One business received major damage, while 18 businesses had minor damage. The business that received major damage was a commercial horse-riding ranch/western town at the beginning of the tornado path. Damage was inflicted upon all of the fencing, two trolleys, and 18 tables. One of the biggest buildings on the site was twisted and turned. A donkey was killed, four hayride wagons were lost, and 25 acres of trees were damaged. The owner of the riding ranch saw the tornado and said it looked like the Fourth of July fireworks finale - there were thousands of lightning streaks in the cone. All together, this tornado uprooted or damaged thousands of trees, and at least three dozen vehicles were damaged or totaled. At Old World Wisconsin, an outdoor museum operated by the Wisconsin Historical Society near Eagle, about 2500 tress were damaged at this site alone, and a few buildings sustained minor damage. Overall, Emergency Management officials estimated that residential damage reached $20,577,500, with business damage around $311,500, bringing total private sector damage to about $20,889,000. A few agricultural buildings were damaged, but loss estimates were not available. Public sector structural damage totaled only about $600, while public sector service costs (non-damage) such as debris clean-up, security and public protection, road protective measures, and other miscellaneous expenses were estimated at $101,965. The starting point location was Lat. 42.86785 Lon.-88.50307. The end point location was Lat.42.87100 Lon. -88.40003. The EF-rating was based on DI 2 (FR12) DOD 6 which suggests wind speeds between 125 to 130 mph. On the WSR-88D Doppler radar at the nearby WFO Milwaukee (MKX), a debris-ball appeared near Eagle within a classic hook echo as the parent thunderstorm moved east. |
| April 1977 | Tornado (F2) | not stated | 2 hurt, $2,500,000 | no account filed |
| August 2025 | Flash Flood | Menomonee Falls | 1 hurt, $89,000,000 | Widespread flash flooding of streets, creeks, rivers, and low lying neighborhoods and homes occurred especially in New Berlin, Brookfield, Butler, Menomonee Falls, Elm Grove, and Muskego. Some of the more notable creeks or rivers that flooded were the Fox and Menomonee Rivers and their tributaries. The Butler Ditch, Jewel Creek, Root River, and other unnamed creeks also flash flooded. For all of Waukesha County, 3 homes were classified as destroyed, 310 homes and businesses sustained major damage, 221 with minor damage and 119 with affected damage. These damages were from a variety of 1st floor flooding, basement flooding, and foundation collapse. Residential sewage backups, and raw sewage released into rivers by many municipalities were common. A small number of complete road washouts and swift water rescues occurred, in addition to dozens of people stranded in their vehicles in deep, still water in low lying areas. More specifically, a partial road washout occurred on Lily Road in Menomonee Falls due to the flash flooding of a tributary of the Menomonee River. The large collapse of a Y-shaped intersection at Campbell Dr. and Campbell Ct. in Menomonee Falls also occurred due to the flash flooding of Butler Ditch. A car was swept away at this intersection but the occupant escaped with minor injuries. 130 St. in New Berlin was partially washed out from the flash flooding of a tributary of the Root River. A swift water rescue occurred on Beres Rd. in New Berlin when a car was swept off the road by floodwaters. Dozens of people were evacuated or relocated from their flooded homes and neighborhoods. Very brief rise into moderate flood stage along the Menomonee River at Menomonee Falls between 1-1:15 AM local time August 10. |
| August 1987 | Tornado (F1) | not stated | 1 hurt, $2,500,000 | no account filed |
| June 2011 | Thunderstorm Wind | Eagle | 1 hurt, $276,000 | A 2-mile wide swath of damage was caused by a microburst associated with a bowing line of severe thunderstorms that tracked from southwest to northeast across a large portion of Waukesha County. Wind gusts estimated up to between 100 to 110 mph (87 to 96 knots) dropped thousands of trees, damaged homes and barns and blew down power lines that left 10,000 customers without power in Waukesha County. One person was injured by airborne tree debris near the Pewaukee and Delafield town borders. A semi-trailer truck was blown over on Interstate-94 in Waukesha County, while two other high-profile vehicles were nearly blown over by the strong winds, but concrete construction barriers saved the vehicles from being completely blown over. |
| October 1996 | Lightning | Chenequa | 1 hurt, $10,000 | no account filed |
| June 1997 | Thunderstorm Wind | Chenequa | 1 hurt, $3,000 | no account filed |
| July 2013 | Lightning | Eagle | 1 hurt | Lightning struck the ground near a group of horse riders in the Kettle Moraine Forest near Eagle. The lightning traveled through the wet ground and passed through two of the horses and one of the riders. The second rider was injured when thrown from her horse after it was struck. |
| July 2006 | Lightning | Waukesha | 1 hurt | A man was injured and taken to a hospital after lightning struck very close to him. It is unknown where he was in the city of Waukesha, nor is the exact time known. He was treated and released from the hospital. |
| August 2006 | Lightning | Muskego | 1 hurt | A women was struck by lightning in a parking lot of a business. She was treated at a local hospital and released. |
| June 1997 | Lightning | Sussex | 1 hurt | no account filed |
| July 1996 | Lightning | Sussex | 1 hurt | no account filed |
| June 2008 | Flash Flood | North Prairie | $62,990,000 | Heavy rains resulted in flash flooding across much of Waukesha County. Water reached depths of 3 feet or more and several cars stalled. This was one of 4 flash floods in Waukesha County that occurred on Junen 7th and 8th. Collectively, each of these 4 flash floods resulted in home and business damage along with some crop losses. It was nearly impossible to break down the damages by flash flood event. Therefore, the collective breakdown for all of Waukesha County is provided in this flash flood event.||The breakdown for residential home losses were: 1433 with minor damage, 188 with major damage, and 1 destroyed (total of $54.632 million for home losses). Business losses totaled $5.462 million. Crop losses were estimated at $1 million. Public sector damage wa|s about $2.9 million. There were several roads and bridges that sustained damage. |
| August 2025 | Flash Flood | Menomonee Falls | $9,000,000 | Widespread flash flooding of streets, creeks, rivers, and low lying neighborhoods and homes occurred especially in New Berlin, Brookfield, Menomonee Falls, Waukesha, Pewaukee, Merton, and Muskego. Some of the more notable creeks or rivers that flooded were the Fox River, Jewel Creek, and their tributaries, as well as some lake flooding. Some flood damage occurred to homes especially near Linnie Lac Lake toward Little Muskego Lake. These damages were from a variety of 1st floor flooding, basement flooding, and foundation collapse. Residential sewage backups, and raw sewage released into rivers by many municipalities were common. A small number of complete road washouts and swift water rescues occurred, in addition to dozens of people stranded in their vehicles in deep, still water in low lying areas. More specifically, one lane of Gold Dr. washed out due to the flash flooding of Jewel Creek in Muskego. Large sections of Barker Road in Brookfield and other nearby roads were closed due to the flash flooding of the Fox River, including the Fox River overtopping the Barker Rd. bridge. Dozens of people were evacuated or relocated from their flooded homes and neighborhoods, which included the Deer Path Subdivision near Minooka Park. A sidewall of the Merton Millpond Dam was damaged but quickly repaired. Many other dams in eastern Waukesha County were at or exceeding their maximum flow capacity, but no dam failures occurred. |
| April 2026 | Tornado (EF2) | Merton | $7,400,000 | Tornado appeared to develop in the Lisbon Oaks subdivision, causing mainly tree damage before intensifying closer to Highway 164. The tornado was at it's most intense near Indian Grass Lane where it caused damage to multiple businesses. The strongest damage was to an insurance car shop port that had a well anchored roof that was completely blown off and found approximated 3 to 4 blocks to the east near Highway 164. Damage then occurred to a church near Wildwood Way and multiple homes along Conservancy Court. Tornado appeared to end near Waukesha Ave along Linda Dr. |
| May 1998 | Thunderstorm Wind | Countywide | $6,700,000 | no account filed |
| June 1997 | Flash Flood | Menomonee Falls | $5,380,000 | no account filed |
| April 2006 | Hail | Sussex | $4,440,000 | Hail sized ranged from 1.00 to 2.00 inches in diameter. |
| April 2006 | Hail | Menomonee Falls | $4,440,000 | Hail sized ranged from 1.00 to 2.75 inches in diameter. |
| April 2006 | Hail | Hartland | $4,440,000 | no account filed |
| April 2006 | Hail | Merton | $4,440,000 | no account filed |
| April 2006 | Hail | Sussex | $4,440,000 | no account filed |
| July 2006 | Flash Flood | Waukesha | $3,000,000 | A 1-in-a-100-year flood occurred in and around the city of Waukesha after a heavy rain of 3 to 5 inches within a 2-hr period. The heavy rains were the result of slow-moving or back-building thunderstorms that essentially sat over the same area. There were no reports of injuries or deaths. Numerous roads and yards were flooded with water depths of 1 to 5 feet. Many vehicles were stalled in the deep waters or were damaged. There were numerous reports of flooded basements of homes or businesses or apartments. The roof of one business in downtown Waukesha collapsed due to the weight of the heavy rains. The Fox River in downtown Waukesha exceeded its 6-foot flood stage by 6 inches, and then quickly subsided. Some nearby farm fields reported washed out sections and crop losses. The Expo Center sustained damage as well to several of its buildings. The basement of the downtown Waukesha Fire Department flooded to the depth of 5 feet. This flooding was the result of a collapsed trench outside the building where a new addition was under construction. At one point, Waukesha city officials warned motorists to stay away from the city, and some officials thought the July 27th flooding was the worst they could remember. WSR-88D Doppler radar rainfall estimates indicated that up to 5 inches fell over the northwest portion of the city of Waukesha, tapering off to 2 inches on the far south side of the city where STH 59 is located. One unofficial rain gage catch was 4.25 inches on the north side of the city, which matched the radar estimate. It is nearly impossible to assess the monetary amount of the flash flood damage, therefore, the amount posted in the header strip of this event is only a rough estimate. |
| July 2010 | Flash Flood | Menomonee Falls | $2,900,000 | Thunderstorms training over the region produced 4 to 7 inches of rain over Waukesha County. While many sections of the county experienced flash flooding, the north and northeast sections were hardest hit, with numerous roads flooded and basements flooded in Brookfield, Menomonee Falls and Sussex. A trained spotter reported 4 inches of rain in one hour in Menomonee Falls where the heavy rains caused a sink hole to form on Campbell Drive. Rushing water flooded roads in Delafield near U.S. Highway 18, closed STH 59 at STH 164 south of Waukesha, and covered sections of CTH Z, west of Eagle in western Waukesha County. Flooded roads were also reported in Muskego, New Berlin and Oconomowoc. |
| September 2019 | Lightning | Downtown Waukesha | $2,500,000 | Approximately 100 people were displaced when an apartment building was struck by lightning causing a fire. The 42 unit apartment building was a total loss. One resident was rescued from the third floor and one fireman was injured. Two residents were also injured. |
| July 1987 | Tornado (F1) | not stated | $2,500,000 | no account filed |
| June 1977 | Tornado (F3) | not stated | $2,500,000 | no account filed |
| August 2002 | Thunderstorm Wind | Waukesha Co Arpt | $2,000,000 | no account filed |
| October 1996 | Hail | Mukwonago | $1,200,000 | no account filed |
| November 2005 | Lightning | Hartland | $1,070,000 | no account filed |
| August 2025 | Flood | Menomonee Falls | $1,000,000 | Widespread flooding of streets, creeks, rivers, and low lying neighborhoods and homes continued over the eastern half of the county and was aggravated by additional showers and storms. The greatest concentration of flooding was in New Berlin, Brookfield, Butler, Menomonee Falls, Waukesha, Pewaukee, Merton, and Muskego. Some of the more notable creeks or rivers that flooded were the Fox River, Menomonee River, Jewel Creek, Butler Ditch, Root River, and their tributaries, as well as some lake flooding. Some flood damage occurred to homes especially near Linnie Lac toward Little Muskego Lake. These damages were from a variety of 1st floor flooding, basement flooding, and foundation collapse. Residential sewage backups, and raw sewage released into rivers by many municipalities were common. A small number of complete road washouts and swift water rescues occurred, in addition to dozens of people stranded in their vehicles in deep, still water in low lying areas. More specifically, one lane of Gold Dr. washed out due to the flash flooding of Jewel Creek in Muskego. Large sections of Barker Road in Brookfield and other nearby roads were closed due to the flash flooding of the Fox River, including the Fox River overtopping the Barker Rd. bridge. A partial road washout occurred on Lily Road in Menomonee Falls due to the flash flooding of a tributary of the Menomonee River. The large collapse of a Y-shaped intersection at Campbell Dr. and Campbell Ct. in Menomonee Falls also occurred due to the flash flooding of Butler Ditch. 130 St. in New Berlin was partially washed out from the flash flooding of a tributary of the Root River. Dozens of people were evacuated or relocated from their flooded homes and neighborhoods, which included the Deer Path Subdivision near Minooka Park and homes near Linnie Lac. A sidewall of the Merton Millpond Dam was damaged but quickly repaired. Many other dams in eastern Waukesha County were at or exceeding their maximum flow capacity, but no dam failures occurred. River flooding along the Lower Fox River in Waukesha peaks during the evening of August 11, with a 8.62 foot crest in moderate flood stage occurring at 5:15 PM local time. Moderate river flooding continues along Lower Fox River in Waukesha through the morning hours of August 13. In moderate flood stage, water from the Lower Fox River approaches the base of the Bastow St and Bank St Bridges in downtown Waukesha, in addition to some homes in the Bethesda Court area about one half mile south of downtown Waukesha. Water also inundates the Frame Park area, with waters at least 3 feet deep on land near the shoreline of the Lower Fox River. Water approaches Corrina Blvd and Union St to the south of downtown Waukesha. |
| June 2010 | Tornado (EF1) | Big Bend | $430,000 | This EF1 tornado affected the Big Bend and Muskego area, and spun up a little more than 2 miles north of Big Bend about 1/10 of a mile southeast of the intersection of Interstate 43 and STH 164. The tornado moved east, dissipating about 1/2 mile south of Tess Corners, just northwest of the intersection of Woods Road and Durham Drive. The roof of the Tess Corners Fire Department tore off, and the U.S. Post Office building in Muskego was damaged when an air conditioning unit was blown off the roof. Several post office vehicles were also damaged. The building housing Muskego Beer and Liquor was badly damaged when a wall collapsed and destroyed half the building. All together, 35 residential dwellings were minimally affected, and 41 homes sustained minor damage. Seventeen businesses were minimally affected, and 1 sustained major damage. Some crops were damaged, but no information on loss estimates was available. Total estimated private sector damage was about $430,000. Public sector structural damage totaled about $15,000. Additionally, other public service (non-damage) costs totaled $65,000; which included $45,000 for debris clearance, $10,000 for protective measures, and $10,000 for road systems. Hundreds of trees were uprooted or damaged. Starting location point was Lat 42.91015 Lon -88.21483 with the ending point Lat 42.91118 Lon -88.09850. The EF-rating was based on DI 27 (TH) DOD3 which suggests a wind speed of 105 mph. The average path width was 90 yards. |
| October 2002 | Thunderstorm Wind | Oconomowoc | $300,000 | no account filed |
| August 2002 | Lightning | Elm Grove | $250,000 | no account filed |
| August 1985 | Tornado (F1) | not stated | $250,000 | no account filed |
| May 1982 | Tornado (F1) | not stated | $250,000 | no account filed |
| June 1981 | Tornado (F2) | not stated | $250,000 | no account filed |
| June 1980 | Tornado (F3) | not stated | $250,000 | no account filed |
| July 1972 | Tornado (F1) | not stated | $250,000 | no account filed |
| June 1969 | Tornado (F2) | not stated | $250,000 | no account filed |
| May 1965 | Tornado (F1) | not stated | $250,000 | no account filed |
| August 2000 | Lightning | Pewaukee | $210,000 | no account filed |
| May 2008 | Lightning | Genesee | $200,000 | Lightning struck a nearly 100-year-old church in/near Genessee on State Highway 83, and the resultant fire destroyed the structure. The time of this event andn damage amount are broad estimates. |
| August 2007 | Lightning | Waterville | $200,000 | Lightning struck the roof of a church, started a fire, and damaged the church's sound system, computer system, and natural gas lines. An automated fire-sprinkler system limited the amount of fire damage. |
| July 2000 | Flash Flood | Hartland | $200,000 | no account filed |
| July 2000 | Thunderstorm Wind | Brookfield | $200,000 | no account filed |
| August 1997 | Thunderstorm Wind | Muskego | $200,000 | no account filed |
| August 2021 | Thunderstorm Wind | Oconomowoc | $150,000 | Numerous reports of a number of large trees snapped and uprooted trees across Waukesha County. Winds were estimated to be upward of 60 mph, with locally higher gusts across the southern portion of the county. Wind measurements near Eagle, WI of 68 to 77 mph were observed. A large tree fell on a house causing significant damage near Eagle, WI. A business marquee sign was knocked over in Waukesha. Hail of three-quarters of an inch was also observed. |
| August 2008 | Lightning | North Prairie | $150,000 | Lightning struck the roof of a home on Lakecrest Court. The fire resulted in major damage and the house not inhabitable. |
| July 2000 | Thunderstorm Wind | Dousman | $150,000 | no account filed |
| June 1997 | Lightning | Waukesha | $150,000 | no account filed |
| August 1996 | Lightning | New Berlin | $150,000 | no account filed |
| June 2009 | Flash Flood | Downtown Waukesha | $120,000 | Numerous reports of flash flooding were received from the Waukesha to Brookfield and New Berlin areas. A couple gravel shoulder washouts were reported, and some minor damage to basement contents occurred. Water depths on roads reached 1 to 3 feet. A water control facility in New Berlin was damaged by flood waters ($100K). |
| July 1997 | Lightning | Brookfield | $105,000 | no account filed |
| June 2016 | Lightning | Oconomowoc | $100,000 | The roof of a home was struck by lightning with a resultant fire. Smoke and water damage to the home is extensive. All occupants escaped safely. |
| September 2010 | Lightning | Marcy | $100,000 | Lightning struck a house in Brookfield causing a fire in the attic. The lightning strike blew holes in the chimney and the roof of the house. Residents in the home at the time of the strike had escaped by the time firefighters arrived on the scene. |
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