MONTREAL -- Prime Minister Justin Trudeau was one of many Canadians who joined millions around the world Saturday night in turning off their lights for Earth Hour.

Government buildings and monuments across the country also went dim from 8:30 to 9:30 p.m. local time, including Toronto's CN tower, the cross on Montreal's Mount Royal and Edmonton's High Level bridge.

Trudeau tweeted a photo of himself and his wife, Sophie Gregoire Trudeau, cuddling by candlelight Saturday evening.

"We're all on this planet together," he tweeted, hinting the upcoming federal budget would contain measures to deal climate change.

"Tweeting about .EarthHour is one thing. Tuesday, we'll put words into action with a budget that builds a clean economy for Canada."

Some of Trudeau's cabinet ministers also took to social media. Environment Minister Catherine McKenna posted a series of tweets and International Trade Minister Chrystia Freeland also noted the occasion.

The event's main organizer said the leaders' support was a welcome addition to the 10th edition of the event, which was launched in Australia in 2007 as a way to draw attention to environmental issues including climate change.

"Seeing national, provincial and municipal leaders take part and encourage others to take part shows that Earth Hour is more than a symbolic gesture," said David Miller, CEO of WWF-Canada. "It's a message to change climate change that's heard by those in positions of political power."

He said a record-setting 178 countries and territories participated this year.

Canadians also participated in a range of activities in cities across the country, which ranged from a stargazing event in Westmount, Que., to a low-light skate at Whistler, B.C's Olympic Plaza.

It was not immediately clear how many Canadians took part in this year's Earth Hour. Toronto Hydro tweeted Saturday night that the city's electricity use dipped by 3.2 per cent, which the utility said was the equivalent of taking 36,000 homes off the grid.

PowerStream, which serves nine municipalities north of Toronto, reported a 4.3 per cent drop in electricity consumption during Earth Hour. That was down slightly from the six per cent reduction achieved last year.

The City of Edmonton tweeted Sunday morning that the city decreased its energy use by 2.5 per cent.

While Earth Hour grew to include 7,000 cities worldwide last year, some say the event has been losing steam in recent years, at least in Canada.

BC Hydro, for example, said British Columbians reduced the provincial electricity load during Earth Hour by just 0.2 per cent last year -- much less than the two per cent reduction recorded in 2008.

Miller says critics who measure the event's success in megawatt hours are missing the point.

He said the event's goal is to raise awareness, have fun, and celebrate recent successes such as the international co-operation shown by global leaders at the Paris climate conference.

He said political leaders seem to be getting the message that Canadians care about climate change.

"Now we need to see it reflected in action," he said.