Part of these storms may even slip across the border and into southwestern Ontario, putting forecasters on alert. As the storms track into this unstable environment, they are expected to strengthen and organize. Advertisement AdvertisementAdvertisement AdvertisementEssentially, there are two outcomes we could see on Tuesday:Scenario One: Severe weather remains south of the border. Scenario Two: Severe weather grazes southwestern Ontario by the afternoon to early evening hours. Southwestern Ontario Tuesday evening forecast storms - Aug. 11, 2026Upper-level smoke from wildfires will further add to the uncertainty, as it could suppress thunderstorm development and severity.