A destructive, two-day tornado outbreak affected the Great Lakes region of the United States and the National Capital Region of Canada in late-September. A total of 38 tornadoes were confirmed, including an intense, long-tracked EF3 tornado that moved along an path from near Dunrobin, Ontario to Gatineau, Quebec, and an EF2 tornado in the Nepean sector of Ottawa. The tornadoes in Ottawa-Gatineau were declared one of the ten most significant weather events of 2018 in Canada by the Meteorological Service of Canada.

Numerous tornadoes touched down in Minnesota on the initial day of the outbreak, including a high-end EF2 tornado that caused major damage in Morristown, Minnesota. Other damage occurred in Eastern Ontario due to downburst winds from the severe thunderstorms. One death was reported as a result of straight-line winds that occurred during the outbreak, and 31 people were injured.

Meteorological synopsis In the Great Lakes region of the United States, a warm front surged in a hot, unstable air mass ahead of a strong cold front on September 20. An enhanced risk of severe weather was issued by the Storm Prediction Center (SPC), including a 10% hatched risk area for tornadoes stretching from southern Minnesota into Wisconsin. Later that evening, a quasi-linear convective system with numerous embedded circulations and bowing line segments produced many tornadoes across southern Minnesota. This included a high-end EF2 tornado that heavily damaged or destroyed many homes in the town of Morristown, Minnesota. Another EF2 tornado damaged the local airport in Faribault. A few tornadoes were also confirmed in Iowa, Wisconsin, and Ohio, and damaging winds from the line of storms also caused significant damage. Embedded downbursts produced destructive straight-line winds of up to during the event. With 25 tornadoes in a matter of hours, this event was Minnesota's third most prolific tornado day on record.

The severe weather threat was expected to move eastward to affect southern Ontario and a part of southwestern Quebec the next day. On September 21, a significant severe weather threat was confirmed across southern Ontario and the Outaouais region of Quebec, with the potential for severe thunderstorms and tornadoes noted.

Severe thunderstorm watches and warnings along with wind warnings and special weather statements were issued across parts of Ontario as early as the pre-dawn hours of September 21, which remained in effect until that evening. The warm humid air mass reached Ontario that morning of September 21, along with localized thunderstorms with heavy torrential downpours in most of the areas across southern Ontario and again later that day during the tornado outbreak. Record breaking temperatures across southern Ontario ranged from the high 20s into the low 30s.Wind gusted to 83 km/h in the Sault, yesterday: Environment Canada. Also confirms tornado in Ottawa area and high temperature records broken in areas of southern Ontario, sootoday.com, September 22, 2018Ottawa International Airport, ON weather historical data for September 21, 2018, Wunderground, September 21, 2018 Tornado watches and warnings were issued by that afternoon.

On the afternoon of September 21, 2018, a localized outbreak of tornadoes impacted eastern Ontario and southern Quebec. During the event, Environment Canada issued numerous tornado warnings as multiple discrete tornadic supercells moved through the area.Tornado warning issued for Ottawa-Gatineau area, CBC News, September 21, 2018 Between 3:30 p.m. and 6:30 p.m. EDT, seven tornadoes, six of which were strong, caused severe damage in and around the National Capital Region of Canada.

The most significant tornado of the event made a direct strike on the small community of Dunrobin in the west end of Ottawa, then crossed the Ottawa River and struck the southern part of Luskville, the northern part of the Aylmer sector, and the Mont-Bleu residential area in the Hull sector before dissipating near the Pointe-Gatineau neighborhood of the Gatineau sector. The Dunrobin-Gatineau tornado was classified as a mid-range, long-tracked EF3 tornado, with peak winds reaching . Approximately 25 people were injured by the EF3 tornado, six of those taken to the hospital and five people had life-threatening injuries. At least 200 buildings were damaged and an unknown number were destroyed along the path. During the event, the long-tracked EF3 tornado that struck Dunrobin and Gatineau was visible on the horizon behind the Parliament Hill buildings in Ottawa.The sky does not look good, Twitter, September 21, 2018 A still image of the funnel was also captured from a live webcam.Live shot of Parliament Hill downtown Ottawa right now. Tornado warned storm cell tracking north of downtown towards Gatineau, Kelly Sonnenburg TWN/trendsmap.com, September 21, 2018 (archived)

A second damaging tornado, rated EF2, caused significant damage in the Arlington Woods, Craig Henry, and Merivale Road residential areas of Nepean, with peak winds of The tornadoes were preceded by severe thunderstorms throughout Ontario and Quebec.Here's how the Ottawa-Gatineau tornadoes formed so quickly, Global News, September 24, 2018Tornado strikes were 'luck of the draw,' says meteorologist, CBC News, September 23, 2018 Five other tornadoes also caused minor to moderate damage in the region, though they remained over remote forested areas and mostly damaged trees and power lines.Map of where the six tornadoes touched down in Ottawa-Gatineau areas on September 21, 2018, CBC News, September 25, 2018UPDATE: Officials increase Friday's tornado count to SIX, The Weather Network, September 26, 2018

The severe weather threat then diminished by late Friday evening, with cool windy conditions.Ontario: Cool down follows damaging wind storm, The Weather Network, September 21, 2018

Confirmed tornadoes

September 20 event + List of confirmed tornadoes in the United States – Thursday, September 20, 2018EF#LocationCounty / ParishStateStart Coord.Time (UTC)Path lengthMax width EF1NE of MiddlefieldGeaugaOH18:23–18:31A building under construction suffered significant damage and tree limbs were snapped. Outbuildings and a house sustained minor damage as well. EF1NE of MiddlefieldGeauga, TrumbullOH18:31–18:41Two single-wide mobile homes were significantly damaged. Otherwise, damage was confined to trees. EF1SuperiorDickinson, EmmetIA22:21–22:28Trees were damaged in town, and a garage was destroyed. A two-story office building at the Superior Ethanol plant sustained major roof damage, broken windows, and partial exterior wall failure on the second floor. A weather station at the plant measured a wind gust. Crops were damaged as well. EF1Northern Granada to S of HuntleyMartin, FaribaultMN22:52–22:59This tornado touched down in Granada, where a house had its roof blown off, a small and unanchored home was shifted off its foundation and leveled, trees were downed, garages were destroyed, and other homes sustained roof damage. East of town, trees were snapped and sheet metal was strewn through fields. EF0Garden CityBlue EarthMN22:58–23:00A weak tornado struck Garden City, downing trees at the fairgrounds. Outside of town, soybean fields were damaged and additional trees were downed. EF0SW of SkylineBlue EarthMN23:04–23:05A weak tornado caused minor tree damage. A house sustained roof damage from a falling tree. EF1Lake ElysianWasecaMN23:19–23:25A house sustained roof loss and total destruction of its garage. The home owner was thrown from the garage into his yard, and sustained minor injuries. Outbuildings were damaged, a grain bin was thrown into a field. Other homes sustained minor damage, and trees were damaged as well. EF0E of JanesvilleWasecaMN23:20–23:21High-resolution satellite imagery confirmed a brief tornado through corn fields. EF1SSW of WasecaWasecaMN23:20–23:30A tornado damaged trees and a silo along its path. EF1SE of Elysian to NE of WatervilleWaseca, Le SueurMN23:25–23:32This tornado struck Waterville, where numerous trees were downed, many of which landed on homes. A one-story home had a large section of its roof torn off as well. Outside of town, tree limbs were snapped. EF1Eastern Waseca to SW of MedfordWaseca, SteeleMN23:28–23:37A silo and a grain bin were both destroyed. A few sheds and outbuildings, as well as many trees and crops, were damaged. EF2Southeastern MorristownRiceMN23:31–23:36This strong tornado touched down in the southeastern part of Morristown, and caused high-end EF2 damage as it impacted residential areas. Many trees were snapped and numerous homes were badly damaged, some of which lost roofs and exterior walls. One home was left with only a few walls standing. The tornado continued to the northeast outside of town, where a turkey barn and outbuildings were destroyed. Crops were damaged as well. EF1N of Morristown to NE of Roberds LakeRiceMN23:35–23:44Many outbuildings were destroyed, and numerous trees were snapped or uprooted along the path. A shed was crushed by a large tree. EF1OwatonnaSteeleMN23:35–23:42Southwest of town, crops and trees were damaged and a barn was destroyed. In Owatonna, power poles and power lines were snapped, a large factory building sustained minor exterior damage, homes had shingles ripped off, and many trees were snapped or uprooted, some of which landed on homes. EF2Northwestern FaribaultRiceMN23:37–23:40Significant damage occurred at the Faribault Airport, where several hangars were destroyed and roughly 80 airplanes were damaged or destroyed. The footings of one hangar were ripped from its frame. Hundreds of trees were downed, and outbuildings were damaged as well. EF1Roberds LakeRiceMN23:40–23:42Numerous trees were snapped or uprooted, some of which landed on homes and cabins. Outbuildings were destroyed, and one home sustained broken windows and considerable roof damage. EF1N of Medford to E of FaribaultRiceMN23:40–23:47Outbuildings, grain bins, machine sheds, and silos were damaged or destroyed along the path. Homes had portions of their roofs torn off, and many trees were snapped or uprooted. EF1S of NerstrandRice, GoodhueMN23:44–23:50A few sheds and outbuildings, as well as numerous corn and soy bean fields, were damaged. A silo lost a roof panel. EF1N of FaribaultRiceMN23:44–23:48Numerous large trees were damaged along the path. EF1S of DundasRiceMN23:45–23:50This tornado damaged power poles and trees, twisted road signs, and left a convergent pattern in a corn field. EF0DundasRiceMN23:46–23:51Pine trees were uprooted and billboards were destroyed to the southwest of town. In Dundas, numerous trees were snapped or uprooted. EF1SE of NorthfieldRice, GoodhueMN23:52–23:57A pizza restaurant housed in a large barn was leveled by this high-end EF1 tornado. Other outbuildings were damaged or destroyed, and trees were damaged. EF0S of WanamingoGoodhueMN23:56–00:05Corn crop was damaged, and tree limbs were snapped, some of which pierced the roof of a machine shed. EF1Southern Cannon FallsGoodhueMN00:01–00:03Numerous trees were snapped or uprooted, with many falling on homes and vehicles. EF0N of Cannon FallsDakota, GoodhueMN00:02–00:05Roofing material was removed from a commercial facility, and a convergent pattern was noted in crops. EF0S of New TrierDakotaMN00:04–00:08Outbuildings were damaged at several farms. EF0NE of ZumbrotaGoodhue, WabashaMN00:09–00:14This tornado struck several farms, destroying grain bins and outbuildings. EF0Prairie IslandGoodhue, PierceMN, WI00:16–00:19This brief, weak tornado caused minor damage. EF0E of EllsworthPierceWI00:27–00:29A barn, sheds, trees and outbuildings were damaged.

September 21 event