OTTAWA -- Prime Minister Stephen Harper paid tribute to members of the Canadian Armed Forces on Wednesday during a rainy Canada Day celebration on Parliament Hill.

"I recently met some of these heroes who defend this country," Harper told the umbrella-toting crowd.

"In the Baltic and in Eastern Europe, they are supporting our friends and allies who face Russian aggression. And, in Iraq and in Kuwait, they are fighting the terrorists there, to keep us safe here."

He went on to reference the shooting of honour guard Cpl. Nathan Cirillo last October.

"As we saw right here in our Parliament, this threat is everywhere today," said Harper, who took in the festivities with his wife Laureen and two children. "But we have faced great threats many times before, and we have overcome them. And we shall overcome them once more. So, let's hear it for the brave men and women of the Canadian Armed Forces."

Harper was joined by Gov. Gen David Johnston and other dignitaries for a noon show celebrating the country's 148th birthday. When the show began, the skies opened on the crowd, which the RCMP estimated about 34,000.

The wet weather meant there was no air show this year. The onstage entertainment was to feature pop artists including Kiesza, Magic and Shad, as well as a tribute to Sir John A. Macdonald performed by actors.

NDP Leader Tom Mulcair's issued a Canada Day statement that hinted at the election on the horizon. He was expected to attend events Wednesday across the Greater Toronto Area, a critical campaign battleground.

"We have many reasons to be proud to be Canadian, but much work remains to be done," Mulcair said.

"The NDP has a clear vision to build a more sustainable society. Canadians can count on the NDP to bring concrete proposals to Ottawa to make life more affordable for families and make Canada a fairer country."

Liberal Leader Justin Trudeau was also spending the day in the GTA and southwestern Ontario. He issued a holiday statement that lauded Canada as "a place of fairness and of opportunity; a place where people from every imaginable country and culture, who speak every language, live and work, and build and thrive together."

Trudeau added: "We are stronger not in spite of our differences, but precisely because of them. For much of the world, Canada represents the most hopeful vision of what the future can look like."