Ferrari driver Carlos Sainz topped a rain-hit practice session for the Belgian Grand Prix.
With persistent rain falling at Spa-Francorchamps, not one driver completed more than eight laps.
Sainz headed the timing charts, half-a-second clear of McLaren’s Oscar Piastri with team-mate Lando Norris third.
Max Verstappen, who is set to serve a five-place grid penalty following a gearbox change, was among five of the 20-strong field who did not complete a timed lap.
Qualifying is due to take place at 5pm local time (4pm BST), but the running is under threat given the bad weather and poor visibility generated by the spray in the Ardennes.
Formula One’s governing body, the FIA, said their priority is to ensure qualifying for Sunday’s main event takes place with other sessions throughout the weekend – including Saturday’s sprint schedule – likely to be sacrificed.
Heavy rain is expected to continue on Friday, and into Saturday with conditions forecast to improve on Sunday. One option is to move qualifying to Sunday morning, as the FIA did in Japan in 2019 when Typhoon Hagibis struck.
If qualifying can not take place, the FIA confirmed the grid for Sunday’s main event will be set by championship order.
Conditions worsened through Friday’s one-hour session with Logan Sargeant crashing out at the midway stage.
The Williams rookie lost control of his car under braking for Les Combes, heading straight into the barrier. The American was unharmed in the accident but the red flags were deployed to recover his stricken machine.
Alfa Romeo’s Zhou Guanyu also grazed the barrier after he ran through the gravel.
The FIA’s decision whether or not to run in the wet conditions will be heightened following the death of 18-year-old Dilano Van ‘t Hoff at Spa-Francorchamps earlier this month.
The Dutch teenager was killed after a crash in a rain-hit Formula Regional European Championship (FRECA) race on July 1.
Published: by Radio NewsHub