Message: Isolated thunderstorms possible

Environment and Climate Change Canada is forecasting a risk of isolated thunderstorms which could lead to high-intensity rainfall, ponding, and increased runoff.

Beginning this evening through mid-day tomorrow (Thursday), rainfall amounts between 15 and 25 mm are forecast across the region, with an additional 10 to 25 mm possible from thunderstorm activity. Continuing Thursday afternoon into early Friday morning, a further 5 to 15 mm of rainfall is forecast with the risk of 10 to 25 mm in convective rain.

Isolated thunderstorms bring the risk of high-intensity rainfall, and local peak hourly rainfall could be up to 15 mm. High amounts of rainfall in a short period of time can lead to increased runoff and flash flooding, particularly in urban areas. Rainfall amounts could be higher in localized areas due to the nature of convective storms.

If the upper ranges of these forecasts are realized, accumulated rainfall could total 50 to 80 mm between this evening and early Friday. However, wildfire smoke aloft could hinder thunderstorm development and/or intensity.

Water levels may elevate into natural floodplain areas and low-lying roadways may be impacted. Soils could be saturated from the rain and may contribute to ponding, increased runoff into watercourses, and possible increased erosion and seepage issues.

Individuals are reminded to avoid watercourses and flooded areas due to dangerous conditions, slippery banks, and cold, swift moving water. Children and pets should be kept away from the water.

The Conservation Authority continues to monitor watershed conditions and will issue advisories to municipalities and media should flood issues arise. Municipal emergency response staff and road superintendents should monitor local conditions closely. Please continue to monitor active weather alerts from Environment Canada.

This message will remain in effect until 12 p.m. on June 6th, 2025, unless otherwise updated.