Fernando Alonso led the way for Aston Martin in Friday's second free practice at the Canadian Grand Prix, the two-time world champion making the most of changing conditions to outpace Mercedes' George Russell on a wet day at the Circuit Gilles Villeneuve.

Alonso clocked a best lap in one minute and 15.810 seconds to beat Russell by 0.462 seconds in an unpredictable and open session that saw Red Bull's defending three-time world champion Max Verstappen struggling again.

The Dutchman managed only four laps and jumped out of his smoking car in the pits midway through a session that offered few clues of what to expect in Saturday's qualifying or Sunday's race.

Home hope Lance Stroll was third in the second Aston Martin ahead of Ferrari's Charles Leclerc, winner of his home Monaco Grand Prix two weeks ago, Daniel Ricciardo of RB, Haas's Kevin Magnussen and seven-time champion Lewis Hamilton in the second Mercedes.

Yuki Tsnuoda was eighth for RB ahead of improving Williams' Alex Albon with Sergio Perez 10th for Red Bull, days after signing a two-year contract extension with the team.

After a rain-hit opening session, which reduced the action to only 35 minutes including just five on slicks, there was an early queue to leave the pit lane as another rainstorm arrived.

"It's coming down much harder now," warned Russell, as Verstappen led the way before pitting immediately to switch from softs to mediums.

A bold lap on soft slicks from Alpine's Pierre Gasly, in 1:29.007, lifted him 5.8 seconds clear of an earlier Hamilton lap.

He trimmed it to 1:24.389 - a full 10 seconds faster than anyone else - and then to 1:20.789 before anyone else began to find any real grip.

As they did, Ricciardo, Alonso and Stroll showed bold speed on softs, the home hero reducing the best lap time to 1:18.662 before Alonso clocked 1:17.835, the top three making light of the conditions.

Verstappen's recent struggles continued with the Red Bull driver pulling his car in and swiftly jumping out. "Can we get the fans?" he asked. "I think I smell a bit of smoke."

By mid-session, the track was declared dry again as Alonso trimmed the best lap to 1:15.810, four-tenths ahead of Russell, Stroll and Leclerc. Verstappen was gone, after only four completed laps as Red Bull organised a wall of mechanics to hide the repair work on an electronics problem from public view.

Rain returned, with 24 minutes to go, sending the drivers back to the pits and most spectators deeper into their hooded waterproof ponchos.

It meant frustration for Hamilton who, according to Mercedes, was on a pace-setting fastest lap before he was blocked at the final chicane by a Ferrari and had to take avoiding action.

All this left the session's meaningful running reduced again with Ocon heading out on intermediates followed by Alonso, Stroll and Norris. The Frenchman had missed the opening session, when Alpine handed his car to reserve rookie driver Jack Doohan.