Thousands of people are taking part in the Enbridge Ride to Conquer Cancer this weekend, on a series of routes involving stops in Toronto, Hamilton and Niagara Falls.

Participants gathered pledges before taking to the roads for the two-day ride, which began Saturday and wraps up on Sunday.

For those taking part this year, it’s a very long and tough ride to the finish on a hot and humid Sunday in which a smog alert is in effect.

Ride participants have been cycling along one of six different routes over the weekend — some of which started and ended in either Toronto or Niagara Falls, and others which began in one city and ended in the other. Each of the routes is over 200 kilometres long, according to organizers.

The participating cyclists spent their Saturday night at a camp at Hamilton's Mohawk College.

Organizers say the event has raised more than $18 million this year, funds which will benefit The Princess Margaret Hospital Foundation.

Now in its fifth year, the Enbridge Ride to Conquer Cancer has raised more than $80 million for Princess Margaret Hospital and $149 million for cancer institutes across Canada since its inception.