Windsor-Essex was the latest county to have a severe thunderstorm warning issued on Sunday evening.
Just after 8:20 p.m., Environment Canada warned that slow-moving showers and thunderstorms had developed along the border with the US.
The storms are capable of producing up to 50 mm of rain. "Heavy downpours can cause flash floods and water pooling on roads," the weather agency warned. "Fast-moving water across a road can sweep a vehicle away."
Alongside possible flash floods the storm could produce large hail and damaging winds.
The Office of the Fire Marshal and Emergency Management recommends taking cover immediately if threatening weather approaches.