One hit the area of Athens near Brockville and another touched down around Summerstown, east of Cornwall.
Environment Canada meteorologist Etienne Grégoire said the tornado at Athens was the stronger of the two, and was likely an F1 tornado — the second-weakest level on the Fujita Scale, which rates the storms from F0 to F5.
Grégoire said he estimated the tornado touched down at about 140 km/h.
In Athens, there was extensive damage, with high winds toppling trees onto homes, cars, hydro poles and roads. A shed was destroyed and a cinderblock chimney also toppled during the storm. Environment Canada spokesman Geoff Coulson said the tornado was about 300 metres wide and travelled three kilometres, causing intermittent damage.
The Summerstown tornado was likely an F0, but it too did extensive damage to trees in the region.
Environment Canada also confirmed a microburst — or localized column of sinking air — near Bellamy Lake, about 30 kilometres northwest of Brockville, Ont. The damage in the area was mostly to trees and vegetation.
Tornado warnings were issued for a dozen communities in Ontario, including south Ottawa, Cornwall and Sharbot Lake.
Warnings had also been issued for the western Quebec communities of Huntingdon and Hemmingford, but were later lifted.
In Embrun, Ont., about 10 hydro poles were knocked down on St. Andre Road. About 6,000 Hydro One customers subsequently lost power, which was later restored.
No injuries or fires were reported as a result of the storms.