McLaren's Lando Norris fastest from Carlos Sainz in rain-affected Montreal first practice

A thunderstorm hit the circuit just over an hour before the opening practice session, with reports of fans being told to leave the grandstands on Montreal's Ile Notre-Dame.

Some took to social media to suggest that those fans queuing at the Metro station, which feeds the island, had been wrongly informed that the practice sessions had been cancelled.

In fact the session began on time at 1330 in Montreal, albeit with the pit lane exit closed due to the huge amounts of standing water on a track which was relaid following last year's grand prix.

It took 23 minutes for the first car to emerge on track, with Lewis Hamilton braving conditions but soon becoming one of a number of drivers to slide around on the wet surface.

Sauber's Zhou Guanyu slid into the barriers on the exit of turn five, briefly bringing out a red flag.

Conditions allowed for very limited running but the sun came out for the second half of the session as Norris topped the charts, just over three tenths ahead of Ferrari driver Carlos Sainz.

Charles Leclerc, winner in Monaco last time out, was third ahead of Hamilton and championship leader Max Verstappen.

Verstappen was one of a number of drivers to venture off the track in the closing stages, with Sauber's Valtteri Bottas suffering a huge slide across the grass.

Rain is forecast to play a part on all three days at Circuit Gilles Villeneuve.

The second practice session begins at 1700 local time (2200 BST).