Fernando Alonso was fastest in second practice after Lando Norris topped the opening session on a day when rain dominated at the Canadian Grand Prix.
As forecast, the weather limited the running during both sessions on Friday and meant conclusions over who has the edge this weekend were difficult to draw.
Eager to get some running in after a wet first session, the drivers were out immediately for FP2 on slick tyres as light rain fell.
Charles Leclerc, winner in Monaco, came out on intermediate tyres, but race control quickly noted the Monegasque for tyre usage because the track had not been declared wet by the race director – it was four minutes later – and was called to see the stewards after the session.
Ferrari were fined 5,000 euros (£4,250) by the stewards.
Canadian former world champion Jacques Villeneuve said on Sky Sports F1: “At that level of racing, that’s not the kind of mistake you can make.
“It’s F1, it’s the pinnacle. Everyone has to be on top form.”
A groundhog – regular visitors to the Canadian Grand Prix – was narrowly avoided by Leclerc as Lewis Hamilton slammed on the brakes behind.
Hamilton was less forgiving when he had to leave the track to avoid Leclerc again at the final chicane, saying: “These guys keep backing up in the final corner.”
Championship leader Max Verstappen returned to the pits with smoke coming from the back of his Red Bull and was forced to end his session early as his mechanics got to work.
The timing sheets had chopped and changed amid the mixed conditions – which had forced several drivers to leave the track – but it was Aston Martin’s Alonso who stood atop the standings as the rain intensified and meant no quicker times would be posted.
George Russell was second for Mercedes ahead of Alonso’s team-mate Lance Stroll.
But, with Verstappen 18th and Lando Norris last, it is unlikely to be a true picture of performance heading into the weekend.
Friday’s second running was slightly calmer than the chaotic opening session.
A thunderstorm hit the circuit just over an hour before first practice, 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 initially closed due to the huge amounts of standing water on a track which was relaid following last year’s grand prix.
When cars eventually took to the circuit, Sauber’s Zhou Guanyu slid into the barriers on the exit of turn five, briefly bringing out a red flag, with Verstappen and Valtteri Bottas among the drivers to venture off track in the treacherous conditions.
As the sun came out, Norris topped the charts ahead of Ferrari duo Carlos Sainz and Leclerc.
Rain is forecast to play a part for both qualifying and the race at Circuit Gilles Villeneuve.
Third practice is at 1230 local time on Saturday followed by qualifying at 1600 (2100 BST).