CatIQ, a Toronto-based catastrophe insurance data provider and subsidiary of PERILS, has released its fourth industry loss estimate for the flooding caused by Hurricane Debby’s remnants. The storm affected Ontario and Quebec between August 9 and 10, 2024.
Insured catastrophe losses in Canada reached a record C$8.5 bn in 2024, nearly tripling the prior year’s total and standing 12 times higher than the annual average of C$701 mn recorded in the first decade of the 21st century.
The latest estimate places insured losses at CAD 2.817 bn, reflecting the market’s outlook six months after the event. This is a slight increase from the third estimate of CAD 2.767 bn issued 90 days after the storm.
The total includes claims for residential and commercial properties as well as vehicles.
CatIQ’s updated report provides a detailed breakdown of property and motor losses by FSA (high-resolution CRESTA Zones). Subscribers also have access to meteorological data, including rainfall totals, damage reports, news coverage, and images documenting the storm’s impact.
Following its regular reporting schedule, CatIQ will release a fifth loss update on August 8, 2025, marking one year since the event.
Hurricane Debby began as a tropical depression on August 1, 2024, moving through the western Caribbean and southeastern US before being pulled north by a large atmospheric trough on August 7. This system steered the post-tropical cyclone toward the Great Lakes, delivering heavy rainfall to eastern Ontario and southern Quebec.
Between August 8 and 10, more than 100 mm of rain fell across a wide area from eastern Lake Ontario through Montreal and along the St. Lawrence River to Quebec City. Some parts of southern Quebec received over 200 mm, causing extensive flooding and severe damage.
Caroline Floyd, Director at CatIQ, noted that while Atlantic Canada is typically more exposed to tropical cyclones, southern Ontario and Quebec frequently experience storm remnants. These systems, guided by the jet stream, bring significant atmospheric moisture into the Great Lakes–St. Lawrence River Basin.
While Atlantic Canada is the more obvious target for tropical cyclone activity in Canada, southern Ontario and southern Quebec often see the impacts of remnant storms, many of which follow similar paths to Storm Debby.
Caroline Floyd, Director at CatIQ
Since 2010, insured losses from remnant tropical storms in Ontario and Quebec have exceeded CAD 500 mn. Before Debby, the largest such event in Quebec was Storm Irene (2011), which caused CAD 101 mn in insured losses. Irene brought 68 mm of rain to Montreal, far less than Debby’s 154 mm.
Floyd added that Hurricane Debby’s remnants had a significant impact on Quebec, where more than 75,000 personal property claims were filed.
The remnants of Hurricane Debby were especially impactful for residents of Quebec, where more than 75,000 claims for personal property damage were filed.
Although the average claim size was similar to the July 2024 southern Ontario flooding, the number of claims was nearly four times higher.
The remnants of Hurricane Debby brought heavy rainfall and flooding to Ontario and Quebec between August 9 and 10, 2024. The storm system, which had weakened after moving through the southeastern United States, was pulled northward by an atmospheric trough. As it reached the Great Lakes, it intensified, drawing in large amounts of moisture.
Eastern Ontario and southern Quebec received significant rainfall, with widespread areas recording more than 100 mm over two days. Some locations in southern Quebec saw totals exceeding 200 mm, leading to severe flooding. Rivers overflowed, submerging streets and damaging homes, businesses, and infrastructure. Montreal and Quebec City were among the hardest-hit urban areas, while smaller communities along the St. Lawrence River also experienced major impacts.
Floodwaters disrupted transportation, forcing road closures and delays in rail services. Power outages affected thousands of homes, and emergency responders carried out rescues as rising water trapped residents in flooded areas.
The insurance industry faced an influx of claims for water damage to homes, businesses, and vehicles. Many properties suffered basement flooding, while others saw structural damage from fast-moving water.
Compared to past tropical storm remnants, Debby’s impact on Quebec was particularly severe. The amount of rain far exceeded previous events like Storm Irene in 2011. The volume of insurance claims filed was also significantly higher than those following the flash flooding in Toronto a month earlier.
In the months following the event, recovery efforts focused on rebuilding damaged infrastructure and assisting affected residents. The financial impact on the insurance industry continued to rise as assessments and claims processing progressed. The flooding highlighted the vulnerability of urban areas in Quebec and Ontario to extreme weather, reinforcing discussions on flood preparedness and resilience.
