Brockville, Ontario, is bracing for heavy rain and thunderstorms that could bring up to 100 millimetres of precipitation through Wednesday morning, July 29, 2026. Environment Canada issued a Special Weather Statement early Tuesday, warning that a low pressure system is expected to stall over the area, leading to multiple rounds of showers and thunderstorms.
Total rainfall amounts of 50 to 100 mm are possible locally, though amounts will vary widely due to the hit-or-miss nature of the storms. As of 10:00 a.m. Tuesday, conditions in Brockville were already 19.8 degrees Celsius with 100 percent humidity and a falling barometric pressure of 100.3 kPa, signaling the unstable air mass moving in.
Residents are urged to prepare for potential localized flooding, especially in urban areas where storm drains may struggle to handle intense downpours. Lower Trent Conservation has issued a Watershed Conditions Statement – Water Safety, effective until Friday, July 31, warning that standing water could happen in areas with poor drainage.
Elevated water levels on Lake Ontario and the St. Lawrence River are adding to the flood risk. Cataraqui Conservation says water levels remain roughly 30 to 35 centimetres above typical summer peaks, making shorelines more vulnerable to storm surge and wave action during heavy rain. The St. Lawrence River at Brockville is currently at 75.03 metres, which is well below the 100-year flood level but still higher than normal for this time of year.
Environment Canada warns that rainfall warnings may be issued as confidence grows about where the heaviest rain will fall. People in the Brockville-Prescott area should stay tuned to weather updates and have a plan in case flooding occurs. For more information on flood safety, residents can visit the Ontario Floods page or contact their local conservation authority.
