A Montreal rally led by Greta Thunberg on Friday attracted 500,000 people, according to organizers.
Schoolchildren were joined by adults as they marched together with the teen activist at the demonstration as part of a global wave of "climate strikes."
Friday's event in Montreal was one of many around the world. In Italy hundreds of thousands of protesters were reported while an estimated 40,000 were in attendance outside New Zealand's parliament in Wellington.
A year after Thunberg began her Fridays for Future movement outside the Swedish parliament in Stockholm, approximately 60,000 people gathered, organizers said. The Austrian capital of Vienna also reported the same number of protesters.
Germany was also a vibrant place for demonstrators. Thousands of people took to the streets, although figures were lower than last week.
Nevertheless, 65 cities announced organized rallies across the country, of which Hamburg was one, where more than 3,000 fought off the rain to make their voice heard, according to police.
In Munich, authorities estimated around 2,000 people marched through the city center, while 1,200 protesters were reported to have taken part in Nuremberg.
But Montreal stole the show. "Not only was it the biggest event in Quebec's history, but it is the biggest event in the world this week," one of the organizers, Francois Geoffroy, told the crowd.