The work, by researchers from the University of Toronto and Sunnybrook Health Sciences Centre, says the risk of drowning outdoors is nearly 70 per cent higher on days when the mercury climbs to 30 Celsius or above.
That would seem intuitive — people flock to beaches and pools when the temperatures soar. But lead author Dr. Michael Fralick says there is public perception that people are most likely to drown during dark and stormy weather, so they may not fully appreciate the risks on nice days.
Fralick and his co-authors drew data from records on 1,243 drownings recorded by Ontario's Office of the Chief Coroner. The deaths took place in the province between 1999 and 2009.
They found that 82 per cent of drowning victims during that time were male, and most were adults. Children and teens aged 17 and under made up 17 per cent of the drownings.
The coroner's office indicated that in about one-third of cases, alcohol may have played a role in the death.
"(It's) not the majority," acknowledged Fralick, who is doing an internal medicine residency at Sunnybrook, one of the University of Toronto's teaching hospitals.
"But if you want to talk about injury prevention and preventing future drowning deaths this is obviously something that is a risk factor and very modifiable."
According to data collected by the Canadian Red Cross, alcohol use in, on or around the water was linked to about half of drownings across the country.
"Alcohol was present or suspected in more than 50 per cent of boating fatalities and is also a frequent risk factor for drownings related to swimming, wading and falls into water," Red Cross spokesperson Gwen Eamer said via email.
Not surprisingly, most drownings took place during the summer months, both in the Ontario study and in national data collected by the Red Cross. The Ontario study said most of the people who drown did so while taking part in recreational activities.
In the vast majority of cases, personal flotation devices — life preservers and belts — were not used. They were either not present (80 per cent of cases) or not worn (11 per cent of cases).
Eamer said a Red Cross report looking at 10 years of drowning trends concluded that up to 90 per cent of all boating-related drownings could have been avoided if the victims had been wearing life jackets or other flotation devices.
Most of the drownings in the Ontario study took place in open water — lakes and rivers. Drownings in public or private pools, quarries and ponds made up only a small proportion of the total over the period.
Fralick says the study points to things people should be aware of to lower their drowning risks.
"I think the take-home message is essentially that warm weather, hot weather, is associated with a significantly increased risk of drowning," he said.
"This study could be the reminder that even though it might be a warm, hot day and the perceived risk might be low, to continue to practise safe aquatic practices including avoiding alcohol, using life jackets, safe boating. Those would be the core messages I'd want to get across."