Much of southern Ontario was under a severe thunderstorm warning Saturday, with some areas are facing tornado watches, according to Environment Canada.

Alerts were issued at 4:45 p.m., warning residents of York-Durham, Belleville-Quinte-Northumberland, Peterborough-Kawartha Lakes, Brockville and Kingston, among others, that "conditions are favourable for the development of severe thunderstorms which may produce tornadoes."

Tornado warnings for the Picton-Sandbanks Park area and Kingston were later downgraded to watches before ending. Belleville, Kingston-Prince Edward and Stirling-Tweed-South Frontenac were also under tornado watches, which have now ended. As of 10:50 p.m. a tornado watch remained in effect for Brockville.

Tornado watches issued earlier for for Pickering, Oshawa, southern Durham Region, Uxbridge, Beaverton and northern Durham region ended by the middle of Saturday evening.

Environment Canada issues watches when "atmospheric conditions are favourable for the development of thunderstorms that could produce tornadoes" and issues warnings "when imminent or occurring thunderstorms are likely to produce or are producing tornadoes."

Environment Canada was also tracking a severe thunderstorm expected to affect most of the GTA, but cancelled that watch by 8 p.m.