Beginning mid-morning, the cold front will move into southwestern Ontario into the Windsor - Sarnia area. By noon, London and surrounding areas will be impacted. The GTA could start to see thunderstorms by the early afternoon.
Rainfall amounts will be around 25 mm for most areas with higher amounts possible in cottage country around Parry Sound.
The severe thunderstorm risk will shift eastward on Sunday to the Kingston - Ottawa - Montreal area.
Although temperatures have been below normal recently, the high humidity is helping to increase the risk of severe thunderstorms which could include hail and strong winds.
The possibility of an isolated tornado exists for the area east from London to Trenton including the Niagara Peninsula and the GTA and as far north as Barrie.