Lewis Hamilton admits the heat in Canada will "change things" having struggled to match Sebastian Vettel's pace in qualifying.
Although Hamilton put his McLaren up into second place on the Montreal grid, the Brit was 0.303s short of Vettel's leading time.
Hamilton, who has qualified on the front row in six of this year's seven grands prix, put his lack of pace down to the higher temperatures seen on Saturday.
And with Sunday's grand prix expected to be the hottest race to date this season, he has a few concerns.
"We just struggled throughout," said the 27-year-old.
"Yesterday we had very good pace, but the conditions were cooler. With it hotter today I really, really struggled.
"Because of that I, for one, didn't expect to be so far up, so I don't know what's now going to happen.
"I've fortunately got myself into a really decent position, but now that it's hotter it's going to change things.
"It's going to be tough, so we just have to do the best job we can, try to maximise everything we do.
"We can still have a really good race and get some really good points from where we are."
Hamilton has yet to win a grand prix this season in a campaign that has seen six different winners in six races.
Asked whether he would be happy with just a solid points-haul on Sunday, he said: "Of course, I want to win, but these guys (Vettel and Alonso) are quicker than me at the moment, so we'll have to wait and see."