Aston Martin's double world champion Fernando Alonso has set the fastest lap in a wet and wild practice at the Canada Grand Prix with both sessions run under a severe weather watch at the Circuit Gilles Villeneuve.

Alonso, 15th in the rain-hit first practice, took advantage of early dry conditions in the second with the Spaniard clocking a time of one minute and 15.810 seconds around the island circuit almost a half second ahead of Mercedes driver George Russell.

"It was difficult to take many learnings into the rest of the weekend as each lap the conditions were changing," said Russell. "First it was spitting, then it was drying, then it was raining again.

"The car was feeling good overall, but we will only learn about our position relative to others tomorrow."

Canadian Lance Stroll, who grew up in Montreal and whose father owns the team, brightened up a dreary day for the home crowd by posting the third best effort ahead of Ferrari's Charles Leclerc, winner two weeks ago in Monaco.

It was a promising start to the weekend for Ferrari with Leclerc third best in the morning session behind teammate Carlos Sainz, who was 13th best later in the afternoon.

Two teams that don't routinely feature at the top of the time sheets made surprise appearances with Red Bull's Daniel Ricciardo fifth ahead of Haas's Kevin Magnussen.

Seven-times world champion Lewis Hamilton was seventh fastest for Mercedes.

McLaren's Lando Norris, who topped the first session, finished at the very bottom of the second.

His Australian teammate Oscar Piastri, fresh from his runner's up spot at Monaco last time out, was sixth quickest in the opening session and then 16th in second practice.

"I think it's impossible to tell who's where today," McLaren CEO Zak Brown told Sky Sports. "Maybe we'll find out tomorrow.

"There's no reason why we shouldn't be very competitive, as we have been pretty much all season.

"The last three races have been super strong so I see no reason why we can't be here.

"With these changing weather conditions, if this is what tomorrow and Sunday is like, then it's going to be about being in the right place at the right time."

Red Bull's triple world champion Max Verstappen, who was dominant in Montreal a year ago leading every lap from pole, did not get his bid for a Canada hat-trick of wins off to a smooth start.

After clocking the fifth best effort in the first session, the Dutchman could manage only four laps in the second before pulling into the pits saying on the radio he smelled smoke coming from the car.

Alpine's Australian reserve Jack Doohan took part in first practice, stepping in for Esteban Ocon, who was told earlier this week the Renault-owned outfit would not be renewing his contract for next season.

But Doohan, the son of five-times 500cc motorcycling world champion Mick and a possible replacement for the Frenchman, failed to post a time.

Ocon was back in the car for Friday's second free practice and was 11th.

Both sessions were run under changeable threatening conditions.

About an hour before first practice a ferocious storm rumbled across Ile-Notre Dame drenching the island circuit and pelting spectators with hailstones as they were evacuated from the stands delaying the start of the session by 20 minutes.

The afternoon practice got underway in dry conditions but with ominous dark clouds, drivers lined up early to get out on the track to try and get in some laps on the slicks before the rain arrived.