Revellers brave the heat to celebrate Canada Day on Parliament Hill

Concerts and fireworks planned for Canada's 151st birthday on Parliament Hill are taking place on one of the hottest summer days the nation's capital has ever seen.

The temperature in Ottawa on Sunday was forecast to hit a high of 36 C. By early afternoon, the humidex had hit 47 C, matching the all-time high for Ottawa, which occurred on August 1, 2006. 

As of 10 p.m., paramedics on Parliament Hill and other special event sites had treated 101 people, mostly for heat-related problems. Eighteen people were sent to hospital for heat and heart issues. 

The number of revellers also dropped as temperatures went up. At 11:30 a.m., there were 6,200 people on Parliament Hill. Just after 1 p.m., there were 3,500. 

There was no wait to get through security, but once on Parliament Hill, thirsty partygoers had to wait in line at water stations to refill bottles. Many made use of misting stations and a snow machine to cool off. 

The highest recorded temperature for the city on July 1 was 36.7 C in 1963, when the annual birthday celebration was called Dominion Day.

The City of Ottawa's public health agency is advising participants celebrating Canada Day in the city to make plans to seek shelter from the sun to avoid overexposure, avoid strenuous activities, drink plenty of fluids and limit or avoid caffeine and alcohol.

Even with the heat, Parliament Hill visitors said things went smoothly. 

Stacey Nunes, from Ottawa, visited the Hill last year for Canada 150 celebrations. He said he waited in line for two hours before getting in for the evening show. 

Today was "much easier, very well organized," he said. 

"Last year there was confusion, caused by the rain, caused by the amount of people, caused by a lot of the excitement, but, you know, people made it through. We had a great time in line last year, singing O Canada, talking to people from around the world, but it was not easy to get on the Hill."

Winnipeg's Sarah da Silva, along with her mother and son, staked out a spot on the lawn with a view of the stage and within range of the misters cooling the crowds. 

She said it took only about two minutes to get through security. 

"Definitely more airport feel than Canada Day feel at first, but you know what? It's better to be safe than sorry," she said. 

One person who didn't make an appearance at the Parliament Hill celebrations was Prime Minister Justin Trudeau. Trudeau was instead spending the day on a cross-country tour, with stops in Leamington, Ont., Regina and Dawson City, Yukon.

The prime minister instead addressed revellers gathered on Parliament Hill on Sunday morning via video, thanking residents and Canadians for standing up for one another and for Canadian values.

"This is who we are, we're there for each other in times of difficulty, in times of opportunity. We lean on each other and we stand strong and that's what we do from coast to coast to coast," Trudeau said.