Ahead of today's sole practice session the air temperature is 17.3 degrees C, while the track temperature is 20.5 degrees. There is a 30% chance of rain.

Both sessions yesterday were affected by the weather, while a red flag stoppage courtesy of Magnussen, did little to help. Consequently, the teams were unable to complete little long run mileage and are therefore short on vital data.

Further complicating matters is the fact that a number of drivers will take grid penalties after taking on new engine components, among them title protagonists Verstappen and Leclerc, both of whom will start from the back of the grid.

While this might appear to favour Mercedes, the German cars were off the pace, with Alpine and McLaren appearing to be the greater threat.

However, how many times have we seen Mercedes turn a poor Friday into a superb Saturday, so let's not write-off the German team's chances. That said, we know from experience that, tyre-wise, the German team struggles in cooler temperatures, which means it could well be compromised.

Ferrari is looking strong, but with that penalty it appears that much will depend on Sainz, who will be only too keen to take advantage.

Similarly Perez at Red Bull though the Mexican didn't impress yesterday.

The lights go green and Hamilton leads the way, followed by Stroll, Vettel, Perez and Albon.

Both Mercedes running different spec rear wings, Hamilton opting for the lower downforce option.

As more drivers head out, all three compounds are in use, though Ocon and Norris are the only drivers on hards.

Hamilton posts a 51.794 on his softs, but Perez (softs) responds with a 50.960 and Albon (softs) 50.050.

A 50.089 sees Ricciardo go second, ahead of Verstappen, Latifi, Perez and Hamilton. Ocon goes sixth on hards, albeit 1.3s off the pace.

Alfa goes 1-2, with Zhou posting a 47.795 and Bottas a 47.922. both are on softs.

"Massive D-rate out of the last corner," reports Russell, the Briton 3s off the pace after just two sectors.

He crosses the line at 52.315 to go 12th.

As Vettel goes third (49.268), Ricciardo switches to the hards.

After 13 minutes Leclerc, Magnussen and Sainz have yet to appear, while Alonso and Schumacher have been out but haven't posted times.

As the Alfa Romeo pair continue to top the timesheets it's worth noting that while Bottas is due to start from the back tomorrow, teammate Zhou is also understood to be taking on a new power unit and a similar penalty.

A 48.746 sees Stroll go third, the Canadian maintaining the impressive form shown yesterday.

Twenty-two minutes in and Magnussen finally emerges, leaving the Ferrari pair as the only no-shows.

We have a small issue, we need to box," Schumacher is told, as teammate Magnussen goes third with a 48.004.

The Ferraris head out on to an almost deserted track, the only other drivers in action being Magnussen, Perez and Albon.

Quickest in the second and third sectors, Sainz crosses the line at 46.461. Leclerc responds with a 46.890.

However, Albon goes quickest in S1. Maintaining a strong pace, the Williams driver crosses the line at 46.836 to go second, just 0.375s down on Sainz.

Hamilton improves to fourth with a 47.366.

At which point the FIA confirms that Zhou will indeed be starting from the back of the grid after taking on new engine components.

Perez, a possible contender for pole under the circumstances, goes quickest with a 45.972.

Quickest in S2, Verstappen fails to improve after a mistake by Zhou further ahead brings out the yellows.

Vettel improves to tenth with a 47.310.

Previously the pace-setter, Zhou has now slipped to 14th in the standings. Perez is quickest, ahead of Sainz, Leclerc, Albon, Bottas, Stroll, Gasly, Latifi, Vettel and Hamilton.

Russell improves to seventh with a 47.089, but remains over a second off the pace.

Verstappen goes quickest with a 45.480 as he is warned that he previously went through a yellow. The Dutchman insists that there was no flag. Ironically, the yellow was triggered by his teammate.

Norris improves from 17th to 2nd with a 45.965, but is demoted when Sainz posts a 45.824.

"This is going to be one of the most complicated qualifying sessions of the year strategically, as so many drivers are taking grid penalties," warns Pirelli.

"The engine brake is so..." shouts Tsunoda before continuing with a string of expletives.

Latifi goes quickest in S1, as the stewards reveal that they have noted Verstappen's yellow flag incident.

Russell goes fifth (46.071), Hamilton eighth (46.769) and Latifi ninth (46.811).

Leclerc is warned that he losing out in Turns 1 and 5. However, he loses a heap more time when he goes off at Turn 13 and into the gravel.

"I'm back out," he tells his team, "I don't think the car is damaged."

Nonetheless, the session is red-flagged.

Replay shows he hit a bump whilst pushing hard and lost the rear, spinning off into the gravel. He touches the barrier, necessitating a new front wing.

The session resumes with 4 minutes remaining.

Ocon leads the way, followed by Zhou, Magnussen, Stroll and Verstappen... at which point light rain begins to fall.

Having reviewed that yellow flag incident, the stewards deem that no further investigation is necessary.

All are on track bar Leclerc, Ricciardo and Schumacher, who hasn't been since his sensor issue.

Verstappen is warned of "light rain at Turn 10". Undaunted, the Dutchman goes quickest in S2, crossing the line at 45.184.

Moments later however, Perez responds with a 45.047.

Alonso goes fifth, while Vettel goes eighth.

The session ends. Perez is quickest, ahead of Verstappen, Sainz, Norris, Alonso, Russell, Leclerc, Vettel, Ocon and Gasly.

Ricciardo is eleventh, ahead of Hamilton, Latifi, Albon, Bottas, Stroll, Magnussen, Tsunoda, Zhou and Schumacher.

Check out our Saturday gallery from Spa here.