The rainy conditions in Montreal set the stage for a challenging and unpredictable practice session. With small puddles forming around the circuit, the track temperature was a chilly 17.5 degrees Celsius as the session began.
Nico Hulkenberg and Kevin Magnussen from the Haas team were the first to venture out on the damp track using full wet tires. Hulkenberg initially set the fastest time with a 1m34.889s, but Magnussen quickly topped that with a lap of 1m34.797s.
However, it was Fernando Alonso who made an impressive start with a time of 1m32.217s, despite encountering Yuki Tsunoda on the exit of the hairpin. Nevertheless, Esteban Ocon managed to surpass Alonso by clocking a time of 1m31.428s.
As the times continued to drop, Hulkenberg briefly reclaimed the top spot with a lap of 1m30.721s. But his reign was short-lived as Tsunoda snatched the position with a time of 1m30.685s.
Ocon fought back and climbed to the top of the timesheets with a lap of 1m30.348s, despite struggling with the final chicane. However, Alonso, who was on intermediate tires, set the best first and second sectors but struggled in the hairpin braking zone.
Carlos Sainz joined the battle and clocked a time of 1m27.245s, moving ahead of his compatriot Alonso. But his lead was short-lived as Leclerc emerged with a stellar lap of 1m26.733s, putting him in the top spot.
Verstappen, despite complaints about his downshifts, delivered a stunning lap of 1m24.977s to take the top spot. But Leclerc quickly responded and shaded Verstappen by 0.127s to reclaim the bragging rights.
Verstappen improved on his next timed lap, setting a time of 1m24.192s, extending his advantage even further.
As the drying line began to emerge, Verstappen raised the bar once again with a lap time of 1m23.779s. He further improved on his next lap, clocking a time of 1m23.154s.
Verstappen‘s gap widened to 1.6s over the field, but Leclerc closed the margin to just over 0.2s. Unfortunately, the rain intensified with 10 minutes remaining, making further improvements impossible.
Pierre Gasly managed to climb up to sixth place after struggling at the bottom of the timing boards earlier in the session. He finished just ahead of home favorite Lance Stroll by a tenth of a second.
Lewis Hamilton completed the top 10 but expressed frustration with the difficult conditions, feeling that the team was wasting time as he struggled to warm up his tires.