This probable tornado touched down at 1:45 pm. No damage was caused, but local pilots reported observing the tornado touch down near the Mountainview Airport.
Figure 1 depicts the surface observations at 2:00 pm EDT, which depicts a low pressure and cold front moving across Lake Ontario. This area of convergence was the focus of thunderstorms in the early afternoon of June 17th.

According to Environment and Climate Change Canada (2018), an F0 tornado touched down at 1:45 pm EDT near Crofton, ON. The path and width of the tornado was not documented by ECCC. The tornado caused no fatalities, injuries or property damage.
Sources
NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 18Z Tue Jun 17 1997. 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/