This year marks the end of an era in the Canadian meteorological community, as David Phillips, Environment Canada's senior climatologist, retired and transitioned to an emeritus status after an extraordinary 56-year career.
Since 1996, Phillips has compiled the annual Top Ten Weather Stories, capturing the year’s most defining weather events. As he steps away, Environment and Climate Change Canada will continue the tradition of delivering the annual ten most impactful weather stories.
Canada’s 10 most impactful weather stories are collectively selected by a Meteorological Services team. Decisions are based on factors including the degree of impact on Canada, including human impact, severity, economic costs, the extent of the area affected, and the event’s longevity as a top news story in Canada and around the world.
The weather of 2024 shattered records as Canada's most expensive year for weather disasters.
It was a soggy summer in Ontario, with several bouts of heavy rain causing significant flooding across parts of the south. Two events particularly stood out, bringing widespread impacts to the Greater Toronto Area on both occasions.
July 15-16
Between July 15 and 16, numerous thunderstorms tracked across southern Ontario. Early on the morning of the 15th, the first cluster of thunderstorms entered southwestern Ontario from the state of Michigan. Several more rounds of storms rumbled their way eastward into the Golden Horseshoe region by the afternoon.
In less than four hours, 50 to 60 millimetres of rain doused the London area, flooding roads and basements, and closing a stretch of Highway 402 west of the city. Further east, over 60 millimetres of rain fell over six hours in the Hamilton and Burlington areas, flooding homes, streets, and businesses.
In downtown Toronto, 25 millimetres of rain fell in under one hour, flooding two subway stations along with parts of Lakeshore Boulevard. And that was not the end of it.
On the morning of July 16, storms lined up across southern Ontario once again, but this time, they aimed squarely at the Greater Toronto Area (GTA). The ground was already saturated from previous downpours. When the storms began, the water had nowhere to go.
Most of the precipitation fell within just a few hours, triggering widespread flash flooding. The heaviest rain fell over parts of Mississauga and Toronto, with 97.8 millimetres filling the rain gauge at Pearson International Airport. Downtown Toronto recorded 83.6 millimetres of rain, and 87 millimetres fell at Billy Bishop Airport, located along the Toronto Waterfront.
Many multi-lane freeways, including the 401, 410, 404, 400, and 427, were flooded. In downtown Toronto, sections of Lakeshore Boulevard and the Gardiner Expressway were also underwater. Calls for emergency services poured in as people were stranded on flooded roadways and trapped in elevators. Police, fire, and emergency medical services, along with Toronto Emergency Management, coordinated an impressive response.
The Don Valley Parkway, a major north-south route that snakes its way alongside the scenic Don River Valley and into downtown, is especially prone to flooding during heavy rainstorms. On July 16, dozens of vehicles became stranded when murky water covered sections of the roadway, leading to 12 water rescues.
Commuters downtown faced chaos as flooding turned staircases at Union Station into waterfalls and nearby subway stations were closed as water surged into Toronto's underground transit system. At the same time, a significant power outage affected nearly 300,000 customers downtown and beyond for several hours.
In Mississauga, the fire department conducted multiple water rescues on flooded roads, and over 100 residents of a nursing home had to be relocated. In the Kitchener-Waterloo-Cambridge area, flood-related calls surged as roads, trails, and parks were inundated. In the City of Kitchener, a section of railway tracks was left suspended in mid-air after the ground beneath it washed away in a rushing torrent of water.
By the time the rain ended, the floods of July 15-16 had caused over $940 million in insured damages across southern Ontario, according to Catastrophe Indices and Quantification.
August 17-18
Just weeks later, between August 17 and 18, a slow-moving low-pressure system brought another round of severe flooding to the region.
The trouble began on the morning of August 17, when a thunderstorm produced a damaging tornado just south of Kitchener in the town of Ayr. The tornado rated EF2 on the Enhanced Fujita scale with winds over 180 km/h, toppled trees, damaged buildings, and tossed vehicles along its seven-kilometre-long track.
Then, thunderstorms bringing torrential rain moved into Mississauga and parts of Toronto. Once again, roads and basements were flooded in the area, with numerous people requiring rescue from stranded vehicles and stuck elevators. One person in Mississauga was rescued after clinging to a light post in a flooded intersection. Segments of major highways were flooded, including the 401, 403, and 410.
Toronto Pearson International Airport received a record-breaking 128.3 millimetres of rain in a single day, where flights were temporarily grounded, causing significant delays. Meanwhile, Billy Bishop Airport, less than 20 kilometres away, stayed dry, highlighting the often-isolated nature of thunderstorm rains.
In Mississauga, things went from bad to worse when more torrential rains impacted the city on the afternoon of the 18th, causing yet another round of flooding. Some motorists were trapped on Highway 410, where a local fire department deployed a small boat to free the occupants from several stranded vehicles.
The floods of August 17 and 18 across the GTA and surrounding regions caused over $100 million in insured losses, according to Catastrophe Indices and Quantification. This brought the combined cost of flood damage across the region to over $1 billion for the year, making it the second-costliest summer in Ontario history for weather-related damage after the Toronto floods of 2013.
Extreme weather events increase with climate change
Alberta experienced four of this year's most impactful events, including another destructive hailstorm in Calgary that caused $2.8 billion in insured losses. This was Canada's costliest weather event in 2024 and the second-costliest overall in our nation's history. While the rising cost of events like these partly reflects our expanding communities and increasing property values, there's a deeper story at play: climate change is accelerating far beyond natural rates, due to human influence. Climate change is, intensifying both the frequency and severity of certain kinds of extreme weather events.
Extreme heat events are becoming much more likely. Results from the Rapid Extreme Weather Event Attribution system show that the heat that scorched the Maritimes in June, western Canada in July, and parts of the Arctic in August was made much more likely by human influence on the climate. In the case of Canada's Arctic, this summer's hottest heat waves were made at least 10X more likely by human-caused climate change.
These extreme temperatures also increased wildfire risk, bringing hot, dry conditions that contributed to the intensity of the wildfires in Labrador, Newfoundland and Jasper, Alberta, that destroyed over 30 per cent of the iconic Rockies town.
Extreme rainfall events, like the atmospheric rivers that struck British Columbia, the severe urban flooding caused by thunderstorms in Toronto, and the remnants of tropical cyclones in Montreal this year, are becoming more likely. As our atmosphere warms, more moisture can feed these storms, increasing the potential for heavy rainfall and excessive flooding.
Nowhere are these changes more dramatic than in the Canadian Arctic, which is warming about three times faster than the global average, with significant impacts on Arctic communities. In September 2024, the Canadian Arctic reached its second-lowest ice coverage on record. By late that month, the northern route of the Northwest Passage saw its lowest ever ice coverage, becoming nearly ice free.
Here are the Top Ten.
