Many Canadians will be spending an hour with the lights out on Saturday as they join people around the world in marking the 10th annual Earth Hour.
The event is aimed at drawing attention to climate change and for people to conserve energy and show support for efforts to reduce greenhouse gas emissions.
Earth Hour takes place 8:30 p.m. to 9:30 p.m. local time.
The World Wildlife Fund has championed Earth Hour since 2007 when it started in Sydney, Australia.
About 2.2. million people and 2,100 businesses across the city participated.
It was deemed such a success that there were plans to make Earth Hour a national event in Australia.
Since then, the event has grown to involve six continents, over 170 countries, and 24 time zones.
In Toronto during last year's Earth Hour, the city saw an electricity dip of 3.2 per cent, roughly the equivalent of 36,000 homes of the grid, according to Toronto Hydro.
The World Wildlife Fund is encouraging social media users to "donate" their Facebook feeds to display messages about climate awareness, or to add an Earth-Hour filter to their Facebook and Twitter profile pictures.