A 66-year-old Toronto woman suffering from dementia was found frozen to death on a Toronto sidewalk Monday, after she left her home in the middle of the night.

She was rushed to hospital without vital signs shortly before 6 a.m. on Monday after she was found lying on a sidewalk on Kennaly Crescent, near McNicoll Avenue and Brimley Road in Scarborough.

She was confirmed dead in hospital a short time later.

Toronto police called the death an avoidable tragedy on Monday, adding that neighbours had heard screams but didn't realize the woman was in distress.

Police said the woman was clearly suffering from hypothermia when she was found only one block from her Scarborough home.

Her husband had woken up at around 2 a.m. and noticed her missing. The family called police after a fervent two-hour search.

Toronto Police Sgt. David Dube said the woman suffered from Alzheimer's disease. She was dressed for the elements but her jacket had been removed. He said it appeared she had fallen and was unable to stand up.

Dube said two neighbours reported hearing screaming at around 2 a.m.

It appeared as if the woman had tried to get out of the cold before her death. Dube said markings on a car and a nearby home's screen door suggest she may have tried to open them.

Dube said foul play is not suspected, but he is surprised people in the area did not offer some sort of assistance.

"I would encourage people to call the police. They wouldn't have to get involved and confront things, but they should call us. That is why we are here," Dube said.

Temperatures in Toronto dipped as low as -20 C overnight, with a wind chill that made conditions even more miserable. The city is currently under an extreme cold weather alert.

Neighbour George Cheang said that he heard screaming early Monday, but thought it was just a family conflict.

"I thought it was just a normal family argument, and I just dosed back to sleep," he told CTV Toronto.

Neighbour Domenico Capotorto said that the woman went missing last year, and she was later found at a nearby mall.

With a report from CTV Toronto's Naomi Parness