Environment Canada is warning people in Cornwall, Ontario to brace for heavy rain and possible flooding over the next couple of days. A Special Weather Statement says 50 to 100 millimetres of rain could fall locally by Wednesday morning, July 29, 2026.
A slow-moving low pressure system is expected to stall over the area, bringing repeated rounds of showers and thunderstorms. The agency says rainfall totals will vary a lot from one place to the next because the storms are convective, which means they can pop up quickly and dump a lot of rain in a short time.
Current conditions near Cornwall show 100 percent humidity and a falling barometer at Saint-Anicet, hints that the atmosphere is juiced up and ready to produce heavy downpours. Environment Canada says rainfall warnings might be issued as confidence in the forecast grows.
The Raisin Region Conservation Authority is watching water levels closely across its territory, which includes Cornwall and South Glengarry, as well as large portions of North Glengarry and South Stormont. The authority is part of Ontario’s Flood Forecasting and Warning Program and has issued flood watches and warnings in the past when similar weather hit the region.
In August 2024, the remnants of Tropical Storm Debby brought 80 to 120 millimetres of rain to eastern Ontario, forcing the conservation authority to issue a Flood Watch. As recently as March 2026, warm temperatures and heavy rain caused snowmelt and flooding, leading to an actual Flood Warning for the same area.
Floods can be the most expensive natural hazard in Canada, causing shoreline erosion, road damage, and power outages. Anyone looking for flood information can visit the Ontario Ministry of Natural Resources and Forestry website or contact the local conservation authority.
