[2] On the early morning of August 19, a low-pressure area was sitting over Northern Michigan with a cold front southwestward.

As shown in the map to the left, there was up to 50 mm (2.0 in) of precipitable water in the warm air mass invading Southern Ontario with a strong southwesterly low level jet parallel to the cold front and the presence of an upper jet-stream.

[1] Severe thunderstorm warnings were sent, mentioning the possibility of tornadoes in view of the radar output and the potential analysis.

It produced winds of well over 100 km/h (62 mph), golf ball sized hail, but mostly heavy rain flooding many parts of the city between 2 and 4 pm.

[1] Finally, another severe storm passing Southeast of Stratford, in the Tavistock area (43°12′45″N 80°50′51″W / 43.21250°N 80.84750°W / 43.21250; -80.84750), gave an F1 tornado with winds between 120 and 150 kilometres per hour (75 and 93 mph) by 3:20 pm.

Convective storm detection showed on weather radars a hook echo, a BWER and a strong mesocyclone but the vortex left the ground after the second tornado.

This wind brings cooler air at the surface and causes a marine temperature inversion which could have been enough to keep the rotation aloft.

[3] The twisters uprooted hundreds of trees, chewed the limbs off of countless others, downed power lines, tossed cars and trucks aside, and ripped into several homes, cottages and barns.

It overflowed storm drains which caused severe basement flooding to many thousands of homes and two floors of the MSC building.