Environment Canada issued a rainfall warning for St. Thomas, Ontario, on Wednesday, March 11, 2026, as heavy rain and potential thunderstorms are expected to create flooding risks across the region.
Forecasters expect between 20 and 40 millimetres of rain throughout the day, though some areas could see even higher amounts if thunderstorms develop. Because the ground is currently frozen or soaked from previous winter weather, it cannot absorb the new rainfall, which significantly increases the risk of flash flooding.
Residents are warned that water will likely pool on local roads and in low-lying areas, and officials are urging drivers not to travel through flooded sections of roadway. People should also watch for potential washouts near rivers, creeks, and culverts while continuing to check for weather updates.
Weather experts note that conditions may change quickly as temperatures are expected to drop significantly later in the day. High winds reaching up to 60 kilometres per hour are also possible, which could make travel more difficult alongside the heavy rain.
