Thunderstorms today across Simcoe County could drop as much as 50 millimetres of rain, according to Environment Canada.
Rain, at times heavy, is expected in Barrie, Collingwood, Hillsdale, Midland, Coldwater, Orr Lake, Orillia, Lagoon City and Washago.
A severe thunderstorm watch is in effect for Innisfil, New Tecumseth and Angus.
Showers and thunderstorms that have affected portions of southwestern Ontario are moving into central and northeastern Ontario.
Heavy downpours can cause flash floods and water pooling on roads. Localized flooding in low-lying areas is possible. Watch for possible washouts near rivers, creeks and culverts.