The 1985 United States–Canada tornado outbreak, referred to as the Barrie tornado outbreak in Canada, was a major tornado outbreak that occurred in Ohio, Pennsylvania, New York, and Ontario, on May 31, 1985. In all, 43 tornadoes were counted including 14 in Ontario, Canada. Ninety people were killed, with 14 deaths occurring in Canada, and 76 occurring in the United States. It remains the largest and most intense tornado outbreak ever to hit this region, and the worst tornado outbreak in Pennsylvania history in terms of deaths and destruction.

Meteorological synopsis

The upper air pattern was conducive for a major severe weather event in the Great Lakes that Friday, May 31. An unseasonably deep low-pressure system at 984 hPa crossed out of the Midwestern U.S. through the day, and then into the Upper Peninsula of Michigan. Very warm air surged in ahead of this system. Temperatures reached the upper twenties in Celsius (approximately ) across much of southern Ontario, in addition to high dew point levels. An unstable atmosphere (surface based lifted indices around minus 6) was the byproduct of this.Environment Canada - Report on the 1985 Barrie Tornado Directional wind shear was also present in the warm sector of the storm, in addition to high helicity values and a vorticity maximum approaching the lower lakes.

The situation was worsened by the presence of copious amounts of moisture, which would allow any storms that could form to become severe rather quickly. Also, this was supportive of the HP (high-precipitation) counterpart of the supercell thunderstorm (Verkaik, 1997). All of this added up to the distinct possibility of severe rotating storms which would be messy, hard to see, and extremely dangerous. What was needed now was a trigger, and that came in the form of a trailing cold front behind the low. Severe thunderstorms and isolated tornadoes had already raked parts of the Midwestern United States (particularly in Iowa and Wisconsin) the day before on May 30, associated with this same cold front (Grazulis, 1990).

The day started off on an active note with the warm front moving northwards. A possible tornado was reported near Leamington, accompanied by golfball-size hail from widespread severe thunderstorm activity in southwestern Ontario. Following the warm frontal passage, skies cleared rapidly and temperatures quickly began to rise. The cold front began crossing Lake Huron towards the noon hour, and with it several thunderstorms developed shortly after 1:30pm EDT, with the northernmost cell soon becoming most dominant. Environment Canada issued a severe thunderstorm warning at 2:25pm for Bruce County (complementing the special weather statement issued early that morning). At around 2:50pm, an F2 tornado touched down briefly in the Lion's Head area (north of Wiarton) before moving out over Georgian Bay and dissipating.

At daybreak on May 31, 1985, a strong area of low pressure was centered near Duluth, Minnesota. A cold front extended south from the low across the western Great Lakes and then through Illinois and Missouri. The low tracked across the northern Great Lakes during the afternoon, while the cold front progressed eastward across Indiana and western Ohio. By late afternoon, temperatures had reached at Cleveland, 82 degrees at Youngstown, and at Erie, Pennsylvania. At the same time, conditions in the upper atmosphere continued to become more favorable for an outbreak of severe weather. By early afternoon, thunderstorms developed in Ontario, Canada, just ahead of the cold front.

Despite a forecast for severe thunderstorms, though, the sun shone relentlessly for most of that Friday because of a fourth element: a stable air mass at about 2,000 feet above ground level, which served as a "lid" on the brew beneath. Then, at 2:50 p.m., the "lid" moved, and huge cumulonimbus clouds, anvil-topped thunderheads, appeared seemingly out of nowhere all along the Ohio-Pennsylvania border. The storms quickly grew into powerful tornadic supercells.

Confirmed tornadoes

+ List of confirmed tornadoes – Friday, May 31, 1985F#LocationCounty / Regional MunicipalityState / ProvinceTime (UTC)Path lengthSummaryF0Leamington areaEssexONF2N of WiartonBruceON1850F3S of HopevilleGreyON1945–2000F3Mansfield areaDufferin, SimcoeON2000–2030Multiple homes were damaged.F4N of Arthur to W of Mount AlbertWellington, Dufferin, Simcoe, YorkON2015–21256 deaths – See section on this tornado — Tornado devastated the town of Grand Valley, where numerous homes and three churches were completely destroyed. The roof of the local library was torn off and thrown . A shopping center on the north side of Orangeville partially collapsed. Severe damage occurred in rural areas as well, including to hydro towers which were toppled by the tornado. This is the longest tracked tornado in Canadian history.Could Canada see a devastating long-track tornado similar to U.S.?, The Weather Network, June 15, 2022F0N of AllistonSimcoeON2030F4NE of Monroe Center, OH to NW of Ivarea, PAAshtabula (OH), Erie (PA)OH, PA205912 deaths – In Ohio, trees and power poles were downed and 10 mobile homes were destroyed. Tornado crossed the state border and struck Albion, Pennsylvania, where an area up to 2 blocks wide and 10 blocks long was devastated. Many homes in town were completely leveled and 9 people were killed. Tornado struck two trailer parks in Cranesville, Pennsylvania, where three other people died.F4BarrieSimcoeON21008 deaths – See article on this tornadoF3SE of Bundysburg to NE of ColebrookeTrumbull, AshtabulaOH2105Forty homes were destroyed, along with multiple trucks, cars, and trailers. Numerous other structures were damaged.F2SE of Linesville CrawfordPA21101 death — Touched down over the Pymatuning Reservoir and moved ashore, damaging numerous homes and campgrounds. The fatality occurred when a woman was crushed underneath a travel trailer. Two trailer homes were swept away, and a barn, a garage, and other structures were damaged.F4SE of Cornelion, OH to SE of Eagle Rock, PATrumbull (OH), Mercer (PA), Crawford (PA), Venango (PA)OH, PA211716 deaths – Long track tornado touched down near the Ohio/Pennsylvania border and caused major damage in and around Jamestown, Atlantic, Cochranton, Cooperstown, Cherry Tree, and Hannasville. Atlantic was particularly hard hit, where a grain mill, a chair factory, a communications tower, a post office, a school building, and multiple homes were destroyed. Five people were killed there. Two homes and 11 trailers were destroyed at a trailer park in the Cherry Tree area, where five additional fatalities occurred. A poultry farm lost 160,000 birds. Numerous other structures including churches, mobile homes, a motel, and two taverns were damaged or destroyed along the path. Tornado caused a total of $5,000,000 in damage.F3S of Saegertown to NE of CentervilleCrawfordPA21232 deaths – This tornado struck a ranger's home at the Army Corps of Engineers Station, with a car being rolled at this location. The fatalities occurred at Centerville.F4SE of Waterford, PA to SE of Panama, NYErie (PA), Warren (PA), Chautauqua (NY)PA, NY2125In Pennsylvania, over 50 buildings were destroyed in the Corry and Elgin areas. One farm was completely leveled in the area, with nothing but a silo left standing. The farmhouse was seen airborne by eyewitnesses. A dump truck was tossed over a house and a wagon was thrown over a mile. 30 head of cattle were killed in the area. Tornado crossed into New York and traversed rural areas before dissipating.F2NE of Dorset, OH to W of Steamburg, PA Ashtabula (OH), Crawford (PA)OH, PA2128Several homes and farm buildings were torn apart along the path.F1Wagner Lake areaDurhamON2140F1Reaboro areaPeterboroughON2205F3S of CentervilleCrawfordPA2212Ten homes, a trailer, and several barns were destroyed. A $500,000 state transportation building was destroyed as well.F3Alma to HilsburghWellingtonON2215–2230Damage was mostly confined to outbuildings.F2Ida areaPeterboroughON2220F3Rice Lake areaNorthumberlandON2225F3E of Jamestown ChautauquaNY2225Homes near Busti, Harmony, Carroll, and Kiantone were torn apart or destroyed.F5W of Newton Falls, OH to W of Mercer, PAPortage (OH), Trumbull (OH), Mercer (PA)OH, PA223018 deaths – See article on this tornadoF4SE of Shamburg to SW of Owls NestVenango, ForestPA22307 deaths – Around 700 structures were damaged along the path, 125 of which were destroyed. At a drug and alcohol rehab center, 14 of 17 trailers were destroyed. The fatalities took place near German Hill, three of which occurred when a car was thrown from Pennsylvania Route 36. F1S of PittsfieldWarrenPA2230F1Minto areaHastingsON2235F2SW of Chaffee to E of HalseyForest, Elk, McKeanPA2250Damage was mostly limited to trees.F1SW of LondonMadisonOH2306F3N of Johnstown to W of West Carlisle Licking, CoshoctonOH23151 death – Several homes and buildings were destroyed, and one person was killed near Fallsburg. Caused $5,000,000 in damage.F3S of TidiouteWarrenPA233032 buildings were damaged or destroyed.F4N of Sabula to NW of Jersey ShoreClearfield, Cameron, Clinton, CentrePA2335Tornado carved a massive path through Moshannon State Forest, downing thousands of trees. The tornado went through Parker Dam State Park in Clearfield County. 13 homes were destroyed, mostly near the beginning of the path.F2S of Salem to W of East PalestineColumbianaOH2335Many homes and farm buildings were destroyed.F1NE of Frazeysburg Muskingum, CoshoctonOH2350F2SW of DotterVenangoPA2354A trailer and five homes were destroyed or badly damaged. A man and his son were badly injured when another trailer was destroyed. Caused $243,000 in damage.F0S of Emlenton Venango, ClarionPA2356F4NW of Brookston to E of Glen HazelWarren, McKean, ElkPA00004 deaths – Severe damage along the path, especially in the Kane area, where three businesses were destroyed, the schools sustained $3,000,000 in damage, and 99 homes were left uninhabitable. A church in the area had only its front steps left, and many vehicles were crushed under collapsed garages. Caused a total of $15,000,000 in damage.F3NW of Darlington to E of Sarverville Beaver, ButlerPA00109 deaths – The Big Beaver Borough Shopping Plaza was destroyed near Beaver Falls. Two people were killed at this location, and over 100 cars were damaged or destroyed in the parking lot. 16 antique cars were destroyed in a garage nearby. At the intersection of highways 588 and 65, the tornado destroyed three homes, a drive-in theater, a service station, and two other businesses. A van was picked up from I-79 and tossed a by the tornado. The family inside was ejected from the vehicle but survived. A trailer park was leveled in the Evans City area, and 40 homes were destroyed between Callery and Mars. Witnesses in the area reported pink insulation and sheet metal falling from the sky prior to the tornado. F1Grippen Lake areaLeeds and GrenvilleON0010Black Friday outbreak: How a 'lost' 14th tornado was found, The Weather Network, May 30, 2015F1W of East SpartaStarkOH0045F1SW of Cedar Mills AdamsOH0105F3NW of Bastress to NE of SpringtonLycoming, Union, NorthumberlandPA01256 deaths – At the Hidden Creek Campground, 48 of the 60 trailers were destroyed, with the rest being damaged. An 83-year-old woman survived the tornado when it threw her mobile home off an cliff and into a tree. In Union County, the tornado destroyed three mobile homes, 8 permanent homes, and 18 vehicles. Five other homes were damaged in the area. In Northumberland County, the tornado damaged or destroyed two businesses, 140 mobile homes, 77 permanent homes, a church, 9 silos, and 28 barns. Thousands of trees were snapped along the path.F0E of Penn Run IndianaPA0153F1N of Norfolk St. LawrenceNY0230F1NW of FreelandLuzernePA0245F1NW of Tobyhanna MonroePA0405Sources: Grazulis (1985)

Grand Valley–Tottenham, Ontario