Thunder Bay, ON F0 Tornado of July 4, 1999

City of Thunder Bay

Witnesses described observing a cylindrical funnel touching down near the city at about 2:30 pm. The tornado snapped and uprooted trees. This was one of two tornadoes to touch down in the province on July 4; the other was an F1 at Bruce Mines, to the east of Sault Ste. Marie.

Figure 1 depicts the surface observations at 2:00 pm, which shows a stationary front over Thunder Bay. This front was responsible for thunderstorms and ultimately this F0 tornado.

Figure 1. Surface analysis at 18Z on July 4, 1999 showing mean sea-level pressure (MSLP) contours, surface observations, fronts and pressure centres (WPC, 2017)

According to Environment and Climate Change Canada (2018), an F0 tornado touched down at 2:30 pm EDT near Thunder Bay, ON. The path and width of the tornado was not documented by ECCC. The tornado caused no fatalities, injuries or property damage.


NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 18Z Mon Jul 4 1999. Retrieved from:

Environment and Climate Change Canada Data. (2018). Canadian National Tornado Database: Verified Events (1980-2009) – Public. Retrieved from: