Ahead of today's second session the air temperature is 20 degrees C, while the track temperature is 27 degrees.
This morning's running was limited due to standing water and a red flag after Zhou clouted the barriers, and in the moments before this session is due to get underway it starts to rain again. Indeed, Race Control helpfully advises that the risk of rain is 100%.
As a reminder, the updates are few and far between this weekend, Red Bull has a new Rear Wing and Front Corner, Mercedes a new Front Suspension and Front Corner and Aston Martin a new Beam Wing.
Williams has new Front and Rear Suspension, RB new Front and Rear Wings, Stake a new Rear Wing and Beam Wing and finally Haas has a new Front Wing, not that they've has much time to test them thus far.
In the final moments of this morning's session there was some dry running, during which Norris set the pace ahead of the Ferraris.
Ahead of the green light the rain ease, and with an eye on the dark clouds in the distance a queue forms in the pitlane. Heading the queue is Verstappen, who, like those behind him, is on slicks.
At which point Russell reports: "It's coming down much harder now".
Verstappen is followed by Perez, Sainz, Russell, Hamilton, Alonso and Stroll.
"It's too wet for the mediums," reports Sainz... so what about softs?
As Leclerc heads out on Inters, Verstappen, Perez and Sainz pit for the green-banded rubber.
Leclerc has been noted for "tyre usage".
Hamilton posts a 34.810 and Gasly a 39.672 - both on softs - as the rest of the field pits.
While Hamilton subsequently pits, Gasly improves to 29.007.
After several minutes, Gasly is joined by Russell, Alonso, Ocon, Leclerc, Piastri and Hamilton, slicks still the order of the day.
Gasly stops the clock at 20.789 as the conditions improve.
Piastri goes second with a 21.914, ahead of Ricciardo, Alonso, Tsunoda and Ocon, Hamilton consolidates his second place with a 21.070.
A 20.704 sees Ricciardo go top as Gasly reports that it is raining more.
Alonso goes top with a 20.599, subsequently improving to 20.451 courtesy of a tow on the straight from Leclerc.
A big slide at the chicane for Magnussen, while Sargeant goes off at the hairpin.
Indeed, a whole load of drivers run wide at the hairpin.
"Leclerc is the slowest person in the last corner," reports Alonso. "No mirrors, typical Ferrari."
Stroll (19.841) makes it an Aston 1-2, his teammate improves to 18.662.
As Albon gets out of shape at the Wall of Champions, Hamilton has a close encounter with a groundhog.
Quickest in all three sectors, Alonso crosses the line at 17.835.
Albon goes second (18.210) but is immediately demoted by Stroll.
A 16.556 sees Leclerc go top as Verstappen pits with a suspected brake issue.
"Can you get a fan," says the Dutchman, "I smell smoke." His crew immediately gets to work.
Alonso retakes the top spot with a 15.810, the Spaniard on softs while Leclerc is on mediums.
Magnussen goes third with a 16.773 as Hamilton posts a 16.908 to go fifth.
"These guys keep backing up in the last corner," says Hamilton.
Seemingly, Leclerc is under investigation for using Inters when the session was not officially declared wet.
With all bar Magnussen and Verstappen on track, traffic is becoming an issue.
Russell improves to second with a 16.273.
As Sainz complains about drivers not using their mirrors the rain begin to fall again, and suddenly the track is almost deserted. Indeed, moments later the track is deserted.
Whatever the weather might do, Verstappen's session appears to be at an end as Red Bull continue to investigate the issue with his car, which is understood to be related to the energy recovery system.
With 19:00 remaining, Ocon heads out on Inters. He is subsequently joined by the Aston Martin pair.
More drivers begin to head out having accepted that conditions are unlikely to improve, and could well continue throughout the weekend.
For the second time this session, Norris under investigation for not following the Race Director's instructions regarding the final chicane.
Leclerc spins at the hairpin. "I don't think that was good for the tyres," he admits.
Can this Ferrari get out of the way... again... every single day," moans Albon of a slow Leclerc in the final chicane.
"What do we do," asks Ocon who feels the track is drying. Alonso concurs.
Despite this, the drivers continue with their Inters, nobody willing to take a gamble on slicks just yet.
Stroll is told to cool his tyres on the straights whenever possible.
The session ends. Alonso is quickest, ahead of Russell, Stroll, Leclerc, Ricciardo, Magnussen, Hamilton, Tsunoda, Albon and Perez.
Ocon is eleventh, ahead of Sargeant, Sainz, Bottas, Hulkenberg, Piastri, Zhou, Verstappen, Gasly and Norris.
Check out our Friday gallery from Montreal here.
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