Valtteri Bottas headed the time sheets in a washed-out final practice session for the French Grand Prix.
The Mercedes driver posted a best effort of one minute and 33.666 seconds in the opening moments before a heavy downpour at the Paul Ricard Circuit.
Defending champion Lewis Hamilton, who topped both practice sessions here in the dry on Friday, was among those who did not set a competitive lap.
Renault’s Carlos Sainz was second in the order ahead of the Sauber of Charles Leclerc. The inclement weather could yet play a role in qualifying which takes place at 16:00 local time.
Hamilton, boosted by a new Mercedes engine this weekend, is bidding to move back ahead of Sebastian Vettel after losing his championship lead at the last round in Canada.
Ferrari driver Vettel heads Hamilton by just one point with 14 rounds still remaining.
Defending champion Lewis Hamilton laid down a marker by dominating practice on Formula One’s return to France.
Hamilton was fastest in both sessions at the Paul Ricard circuit as he bids to usurp rival Sebastian Vettel at the top of the standings.
Ferrari’s Vettel is one point clear of Hamilton, but the British driver and his Mercedes team held the edge in Le Castellet on Friday.
The 33-year-old Englishman lit up the time sheets in the day’s opening running before returning to its summit later in the day.
Hamilton, armed with a new Mercedes engine, posted a best lap of one minute and 32.539 seconds to finish clear of the rest.
Daniel Ricciardo was second for Red Bull, three quarters of a second behind the Mercedes, with his team-mate Max Verstappen third.
Ferrari traditionally underplay their hand on Friday, and Kimi Raikkonen and Vettel finished fourth and fifth respectively.
Vettel, who claimed his third win of the season in Canada a fortnight ago, was more than one second down on Hamilton.
Valtteri Bottas finished seventh in the sister Mercedes after sitting out much of the second session with a water leak on his car.
Earlier in the day, Marcus Ericsson’s dramatic crash brought a premature end to the opening running.
Swedish driver Ericsson lost control at the left-handed 100mph Turn 12, sliding down the long run-off area before hitting the tyre barrier.
His Sauber then started billowing flames from the rear. Ericsson, who could not see the inferno behind him, remained in the car.
Ericsson had to be alerted to the danger over the radio as marshals ran over with fire extinguishers and he hastily leapt out of the car.
The session was immediately red-flagged and Ericsson, 27, emerged unscathed from his charred Sauber.
It marked the first time an F1 car has been on fire since this season’s introduction of the halo, the controversial cockpit safety device which sits above the driver.
There was drama in the second session, too, as Sergio Perez lost his left-rear wheel. The tyre worked its way off the Mexican’s Force India and bounced along the track.
The red flags were deployed with Perez stranded in his three-wheeled car at Turn 7.
McLaren are enduring yet another agonising season, and they have shown no improvement in France.
Fernando Alonso, who completed the second leg in his pursuit of motor racing’s Triple Crown with victory at Le Mans last weekend, was eighth, 1.9 seconds off the pace.
The Spaniard, 36, also spun in the closing moments before limping back to the pits. Alonso’s team-mate Stoffel Vandoorne finished in 13th.
On of the eve of the French Grand Prix, we take a look at the performances of the French drivers so far this season.
Team: Force India
Results in 2018: 12-10-11-retired-retired-6-9
The Evreux native may be off form and also the pace that saw him clinch 18 top-10 finishes last season, but he produced a masterclass over the last two races, finishing sixth in Monaco and ninth in Canada.
With 10th, 11th, 12th and two DNFs in his first five races respectively, Ocon showed flashes of confidence in the last two rounds after a poor start to his second season in F1.
In a long season, the 21-year-old has time on his side to transform his form and push Force India into a high midfield place again. He needs a consistent run if he is to be considered for a potential Mercedes seat in the future.
He’s the leading light of the young generation of French drivers, but Leclerc could be even better in a similar car.
Team: Toro Rosso
Results in 2018: Retired-4-18-12-retired-7-11
The Rouen native continues to cement his reputation as a real talent for the future.
On his second start of the season in Bahrain, he delivered a sumptuous performance to finish fourth, with one slick overtake on Kevin Magnussen midway through the race for one of the standout moments.
In Monaco, he showed superb composure to hold off Nico Hulkenberg to finish seventh. His qualifying performance, making it to Q3 for the first time would have been particularly pleasing for the Red Bull-backed team.
Starting from 16th in Montreal, he showed serious confidence to overtake multiple cars and finish 11th – unable to catch Leclerc in the end for a share of the points but still seriously impressive.
Red Bull will certainly be eyeing up the 22-year-old should Daniel Ricciardo opt to leave at the end of the season.
Results in 2018: 13-12-19-6-10-18-10
The former GP2 and GP3 champion has demonstrated maturity beyond his years in his first three months in F1 and has gone on to score three top-10 finishes in seven races.
With Leclerc’s 10 points added to the two that teammate Marcus Ericsson netted in Bahrain, Sauber now have 12 points in the constructors’ championship – over twice as many as they scored in the whole of 2017.
Although he may struggle with a team who finished last in the drivers’ standings in 2017, he has to start from somewhere and this season is the perfect building block to his future development.
His performances in Baku, Barcelona and Canada are all sure to be the start of something special for the Monaco resident.
Mercedes, Ferrari and Red Bull will all be needing replacement drivers over the next three seasons so now is the perfect time for Leclerc to step up and continue to show his mettle as a rising star and future champion.
Results in 2018: Retired-13-17-retired-retired-15-12
After a torrid campaign, the 32-year-old produced his best performance of the season in the last round in Montreal, finishing 12th.
The Geneva native’s best days may well be behind him, but as the senior driver at Haas, he has showed little to stamp his authority over the first third of this season, with teammate Kevin Magnussen achieving more formidable results in six of the seven races.
Now back in his home Grand Prix as such, Grosjean needs to step up after two high-profile mistakes in Baku and Barcelona have put him under great scrutiny. In Baku, he crashed out under the Safety Car period and spun out on the first lap in Barcelona – earning a grid penalty for Monaco.
Although his result in Canada added some riposte, he needs to bounce back again or he could be under pressure for a seat in 2019.