Temperatures reached the upper twenties in Celsius (approximately 80–85 Fahrenheit) across much of southern Ontario, in addition to high dew point levels.

[4] 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.

Severe thunderstorms and isolated tornadoes had already raked parts of the Midwest U.S. (particularly in Iowa and Wisconsin) the day before on May 30, associated with this same cold front (Grazulis, 1990).

A possible tornado was reported near Leamington, accompanied by golfball-size hail from widespread severe thunderstorm activity in southwestern Ontario.

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.

The low tracked across the northern Great Lakes during the afternoon, while the cold front progressed eastward across Indiana and western Ohio.

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.

While nearly 400 homes were heavily damaged or destroyed, no fatalities were recorded in Newton Falls, due to the storm-readiness of local authorities and its tornado siren.

The Niles Park Plaza shopping center was completely leveled and partially swept away at F5 intensity, with several of the fatalities occurring at that location.

As the tornado struck an industrial area in Niles, large 30-foot tall metal petroleum storage tanks (each weighing 75,000 pounds) were torn from where they were anchored and thrown, some of which were tossed or bounced considerable distances.

The tornado weakened slightly as it tore through the north side of Hubbard and through the center of Coalburg, though many additional homes were still leveled in those areas.

A steel-frame trucking plant in Wheatland was obliterated and partially swept away at F5 intensity, as the building's steel girder frame was mangled into a pile and pushed off of the foundation.

The peak of the outbreak took place during the early evening hours where the strongest and deadliest tornadoes formed across western Pennsylvania and eastern Ohio.

Described as "one of the most impressive tornadic events of the 20th century" by meteorologist and researcher Thomas Grazulis, a massive, high-end F4 tornado tracked for 69 miles (111 kilometers) through dense forest in central Pennsylvania.

[15] Near the beginning of its path, a few homes were heavily damaged and some outbuildings were destroyed, but otherwise, the tornado passed entirely through uninhabited areas in the Moshannon and Sproul State Forests.

People in the area reported pieces of sheet metal and shreds of pink insulation falling from the sky shortly before the tornado arrived.

The second tornado, rated F3, touched down in southeastern Chautauqua County and tracked for 13 miles, striking Kiantone, Carroll and Poland, and narrowly missing Jamestown to the east.

On the ground for approximately fifteen minutes, this tornado tracked a 33-kilometre (21 mi) path of sporadic F3 damage (mainly to outbuildings) from Alma east-northeast towards the Hillsburgh area.

[20] At about the same time the Lion's Head tornado dissipated, two very severe thunderstorms had developed (that likely owed their inception, at least partially, to lake breeze convergence): one to the east of Clinton and another farther to the north, in the Walkerton area.

Shortly after this tornado dissipated, there were hints of another brief touchdown near Angus in the Blackdown Park training area of Canadian Forces Base Borden (north of Alliston).

It formed in southern Simcoe County (Essa Township), less than 10 kilometres (6.2 mi) southwest of Highway 400 and the Barrie city limits.

Despite the tornado's relatively short path length (under 10 kilometres (6.2 mi)), eight people died in Barrie with 155 injured, and as many as 300 homes were damaged or destroyed.

Many power lines and hydro towers were destroyed early in its lifetime (including those used to deliver electricity from the Bruce Nuclear Generating Station to northern and western parts of the Greater Toronto Area).

An elderly woman visiting from Scotland died as the home was destroyed, and a man was killed in his pickup truck on a nearby farm (Bruineman, 2010).

Continuing eastward through more open country, it brushed the northern outskirts of Orangeville about fifteen minutes later (Grazulis, 2001) where the southern portion of the Mono Shopping Plaza completely collapsed (injuring 67 people, one of them seriously).

It then caused extensive damage to approximately fifty buildings (many of which were only recently built) about 2 kilometres (1.2 mi) south of the town of Tottenham at around 5:00 pm.

It just missed the cities of Newmarket and Bradford before lifting west of Mount Albert at 5:25pm, with a path length in excess of 100 kilometres (62 mi), thus becoming a Canadian record that still stands today.

[24] One of the more sobering instances was that of a blind Orangeville-area man whose home suffered a similar fate, following a painstaking 20 years of construction (LeGrand, 1990).

Nevertheless, in the hours following the event, soldiers from "B" and "F" Companies, The Grey and Simcoe Foresters and from Canadian Forces Base in Borden assembled in Barrie to assist in the canvassing of the worst affected areas of the city.

Coincidentally, the latter had barely escaped a tornado itself that day, it having momentarily touched down in the Blackdown Park Training Area before lifting again and passing over hundreds of married quarters.