Rebecca Lake, ON EF2 Tornado of August 4, 2017


This tornado was the strongest and final of three that sliced through the Muskoka Region during the afternoon of August 4. It touched down at around 4:10 pm near Pell Lake, then travelled to the northeast for 9 kilometres. It crossed Highway 8 at Hutcheson Road, chewing through the dense forest as it went. Trees were snapped, uprooted, shorn off at their tops and thrown as the tornado oscillated in width between 100 and 200 metres. The devastation through the forest was immense, with entire tracts levelled. However the tornado was saving it’s most significant human-impacts for the cottages along the shores of Rebecca and Bella lakes.

First the tornado whipped through cottages off of Sunset Farm Trail and Mansell Road on the southwest side of Rebecca Lake. It crossed the water quickly and then ravaged more cottages on the opposite shoreline as it moved inland again along Fairdale Road. A short stretch of forest damage ensued before the tornado reached the eastern tip of Bella Lake. It tore through a row of cottages along Carl Fisher Drive, then crossed the water and made landfall again on the lake’s northeast shore. From there the tornado continued through the forest before it dissipated near Dotty Lake.

Drone footage of part of the tornado's path at Bella/Rebecca Lakes. Ray Jarvis shot this 3 or 4 hours after the storm, when the rain finally stopped. We lifted off from Brian Butt's cottage, then headed towards Swains Bay. Turned around before we got to damage at Craines and Quinlans. Then flew over to Mansell point.

Posted by Cindy Burgess on Sunday, August 6, 2017

Damage across the lakes was devastating. Old-growth forest was levelled and cottages were left buried or crushed by the massive falling trees. In addition, windows were shattered, roofs were torn, sheds destroyed and boats hurled for tens of metres. Had the dense forest of the properties not borne the brunt of the tornado’s winds, it’s likely that the cottages would have been more severely damaged or swept away entirely. Nevertheless, the damage across the lakes was massive and the fact that there were no casualties was remarkable.

Some of the destruction from the tornado on Rebecca Lake. Whole areas of forest leveled in its path.

Posted by Frank Hood on Monday, August 7, 2017

This was the second tornado near Huntsville on the evening of August 4; the first was an EF1 that caused considerable damage on the south side of town. The other two tornadoes that struck this day included an EF1 tornado at Utterson and an EF1 tornado at Huntsville.

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

Figure 1 depicts the surface observations at 2:00 pm EDT, which shows an occluding low pressure system over Sault Ste. Marie, a warm front in northern Ontario/Quebec and a strong cold front moving across southwestern Ontario and Georgian Bay. The cold front became the focus for intense thunderstorms in the afternoon and evening hours of August 4th, which resulted in three tornadoes across Ontario.

Figure 2. Apple Maps satellite data © 1992 – 2020 TomTom.

Figure 2 depicts the visible scare on satellite imagery left by the strong EF2 tornado (red dashed lines).


NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 18Z Fri Aug 4 2017. Retrieved from: