Canada's Defence Minister Harjit Sajjan said the government would provide assistance including military helicopters and personnel to help tackle the fires and reach people threatened by the flames.

The blazes have forced the closure of a number of highways in both directions.

Public Safety Minister Bill Blair said the weather and the wildfires were having a "devastating" and "unprecedented" impact on British Columbia.

"These wildfires show that we are in the earliest stages of what promises to be a long and challenging summer," he said.

The province's medical examiner's office said extreme heat was likely to have contributed to 719 sudden deaths over the past week - a figure it said was "three times more" than the average for the time of year.

"Many of the deaths experienced over the past week were among older individuals living alone in private residences with minimal ventilation," Chief Coroner Lisa Lapointe said in a statement.

Temperatures have been easing in coastal areas of Canada, but there is not much respite for inland regions. The British Columbia Wildfire Service said it was bracing for more wildfires throughout the weekend.

Abnormally high temperatures have been recorded in swathes of North America in recent days.

Experts say that climate change is expected to increase the frequency of extreme weather events, such as heatwaves. However, linking any single event to global warming is complicated.