For the second grand prix running, the second free practice session on Friday was interrupted by heavy rain - just as was the case in Monaco two weeks ago.

As a result, the teams had limited running on the new for 2015 P Zero Red supersoft tyre - nominated together with the Yellow soft compound this weekend - which made its debut at the Monaco Grand Prix. Before the rain came, well into the hour and a half FP2 session, a few drivers were able to sample this new tyre - with some teams exploring the possibility of just a one-stop strategy on Sunday.

However, in order to have some more precise data, the third free practice session on Saturday morning will once again become crucial, as teams finalise their strategies on a track where tyre wear and degradation is traditionally quite low. Weather forecasts suggest that dry conditions are far from guaranteed, meaning that teams will have to think on their feet when it comes to tactics.

Mercedes driver Lewis Hamilton went fastest in FP2 before the rain arrived, setting a benchmark of 1m15.988s on the supersoft tyre: faster than the equivalent top time he set in last year's FP2 at Montreal. Hamilton was also fastest in FP1 on the soft tyre this morning: around a second quicker than the fastest FP1 time last year.

Paul Hembery: "The weather that we saw today was reminiscent of the 2011 Canadian Grand Prix, where torrential rain made for a very entertaining race, won by Jenson Button from the back. It's obviously still early in the weekend but the teams have to be prepared for any potential conditions. The third free practice session tomorrow will become particularly important, as this now represents the only potential opportunity to gather solid long-run data on the new 2015 supersoft tyre, which should be well suited to the tyre demands of the Montreal circuit. Depending on the race conditions, a number of strategies seem possible. However, we will only get a clearer picture after FP3 tomorrow. It's a shame that the fans didn't see much running today, but Canada always produces a thrilling race weekend - we're sure that even the heavy rain here today won't dampen anybody's enthusiasm."

Fact of the day

Montreal has the lowest pit stop time loss of the year, with the cars losing just 17 seconds from the beginning to the end of the pit lane. This might encourage some drivers to opt for a 'sprint' strategy with a high number of pit stops, particularly if the car is fast anyway. The high probability of a safety car means that a flexible strategy can often win the race, making the task of formulating the strategy even more complex for the engineers.

Check out our Friday gallery, here.