Health authorities in Montreal are adding 13 more people to the list of victims of last summer's heat wave, and are urging the city to do more to diminish heat across the densely populated urban neighbourhoods that are home to the most vulnerable.

At least 66 people died as a result of extreme heat on the island of Montreal between June 30 and July 8, 2018, said Mylene Drouin, head of the city's public health authority, on Wednesday. Authorities last year thought the number was 53.

Drouin and medical researchers discovered 72 per cent of those who died suffered from a chronic illness and 66 per cent were over the age of 65.

The statistic that stands out, however, is how 25 per cent of heat wave victims had schizophrenia, a severe form of psychosis.

Drouin said people with schizophrenia need to be better looked after by the health care system but "collaboration is not always easy."

The health authority recommended Montreal do more to identify vulnerable people. Drouin said her office is currently building a registry of those deemed most in need of attention during heat waves.

“It is going to be difficult to have zero deaths but we have space for improvement,” said Dr. Mylene Drouin, regional health director of Montreal Public Health. “We know we can improve the way we do our reaching out, and making sure that people that go and do the intervention are people they trust that can help them to change their habits or bring them to cool places.”

Experts are also suggesting that some neighbourhoods immediately plant more trees and other greenery to combat the heat island effect.

Street corners could have temporary urban gardens equipped with shelters from the sun, she said. These spaces would encourage citizens to interact more outside.

“It's really important to have a greener city. It's great for the quality of life of every Montrealer but there is also a real impact on the health of the citizens,” said Montreal executive committee member Laurence Lavinge-Lalonde.

Previous estimates had suggested up to 53 died in the city when maximum daily temperatures soared to between 31.9 and 35.5 degrees at the end of June and early July.

Last summer's heat wave officially occurred between June 30 and July 5, when daytime temperatures were recorded between 31.9 C and 35.5 C. Drouin's office extended the period of analysis by three days because she said people suffered health effects related to the heat until then.

Researchers analyzed all 328 deaths reported to the coroner that occurred on the island of Montreal between June 30 and July 8, 2018.

They collected information from the medical records of the deceased as well as the circumstances of their death, such as the location, room temperature and the presence of air conditioning, to come up with results.

- With a report from CTV Montreal