Longueuil sits in the St. Lawrence River valley in Quebec, where a humid continental climate produces cold, snowy winters and a spring melt season that is one of the region’s biggest annual flood risks.
On the south shore of the St. Lawrence across from Montreal, the city monitors the same river system during high-water periods. Ice jams during the spring thaw can cause the St. Lawrence and its tributaries to rise suddenly, and summer convective storms add a second flood risk later in the year, both of which Environment Canada tracks using its national radar network. Learn more: Flash Flood Warning Signs on Radar · Open the full Rain Map