At 5:30 pm, this F0 tornado was observed by airport meteorologists as it touched down near the Greater Sudbury Airport, northeast of the city. It caused minor tree damage.
Figure 1 depicts a low pressure in northern Quebec with its associated cold front sliding through central Ontario at 5:00 pm EDT (30mins prior to tornado). This cold front initiated thunderstorms in the afternoon/evening hours.

According to Environment and Climate Change Canada (2018), an F0 tornado touched down at 5:30 pm EDT near Sudbury, ON. The track and the width of the tornado was not documented by ECCC. The tornado caused no injuries, fatalities or property damage.
Sources
NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 21Z Thu Aug 15 1991. Retrieved from: https://www.wpc.ncep.noaa.gov/archives/web_pages/sfc/sfc_archive.php
Environment and Climate Change Canada Data. (2018). Canadian National Tornado Database: Verified Events (1980-2009) – Public. Retrieved from: http://donnees.ec.gc.ca/data/weather/products/canadian-national-tornado-database-verified-events-1980-2009-public/