"In our four biggest provinces, the second wave isn't just starting, it's already underway ... We're on the brink of a fall that could be much worse than the spring," Trudeau said in a televised address, as quoted by the CTV News broadcaster.
"I know this isn't the news that any of us wanted to hear. And we can't change today's numbers or even tomorrow's - those were already decided by what we did, or didn't do, two weeks ago. But what we can change is where we are in October, and into the winter," the Canadian prime minister added.
The World Health Organization declared the COVID-19 outbreak a pandemic on March 11. To date, more than 31.7 million people have been infected with the coronavirus worldwide, with over 974,000 fatalities, according to Johns Hopkins University.
Canada has registered about 150,000 COVID-19 coronavirus cases so far, with more than 9,000 fatalities.