Ahead of today's second practice session, the air temperature is 16.6 degrees C, while the track temperature is 22.8 degrees.

More importantly however... it's raining. Or rather it was.

It began a short while ago during F3 qualifying but subsequently eased off and then stopped, though the dark clouds all around suggest that there is more to come.

Birthday boy, Valtteri Bottas was quickest earlier, ahead of Hamilton, Verstappen, Perez and Stroll, the five covered by just 0.375.

On the other hand, the Ferraris of Leclerc and Vettel were 14th and 15th, behind Raikkonen, while neither of the Haas drivers posted a time and both have had engine changes.

The lights go green, but despite those clouds there is no mad rush to action.

Finally, twelve minutes in, an engine fires up and moments later Giovinazzi - for it is he - heads down the pitlane on mediums.

As the Italian begins his first flying lap of the day, teammate Raikkonen heads out, albeit on the hards.

Giovinazzi posts the benchmark, and at 49.716 the bar is set pretty low.

"More push, more push," he is told.

Raikkonen posts 46.402 despite complaining of a "lot of vibration".

As the Alfas continue on their cool down laps, more drivers head out, including Bottas and the Ferraris.

"Something's not write," warns Norris, "it's misfiring or something."

Ocon posts 45.445 to go quickest (of three) but is demoted when Albon posts 45.212. Ricciardo goes third (45.777), ahead of Kvyat and Gasly.

As Bottas posts 2:20.069 (!), Hamilton heads out.

"Radio check?" asks Russell. "Yes, loud and clear," comes the reply, before adding, "well, loud."

Bottas goes top with a 44.658, with Hamilton posting 45.140 moments later.

The Briton doesn't go second however, because Perez has posted 44.693.

Elsewhere, Stroll and Verstappen are trading fastest sectors. Stroll crosses the line at 44.678 to go second, while Verstappen stops the clock at 44.354 to take the top spot.

As he goes 11th (46.030), Leclerc is told he is only losing out to his teammate in S2. Vettel is 15th on 46.360, the German having had a somewhat scruffy lap.

Hamilton improves to second with a 44.652, 0.298s off Verstappen's pace. That said, the Briton is on hards while the Red Bull driver is on mediums. Bottas' time was also set on the yellow-banded rubber, and other than Hamilton the highest-placed hard runner is ninth-placed Norris.

A 45.225 sees Norris improve to seventh.

Thirty-five minutes in and once again silence descends on the track. While the Haas due have yet to appear, having only competed three laps between them in FP1, Verstappen is quickest, ahead of Hamilton, Bottas, Stroll, Perez, Albon, Norris, Ocon, Ricciardo and Sainz.

Following several more minutes of inactivity, Bottas heads out, followed by his teammate and Albon. All three are on softs.

As Bottas begins his first qualifying sim, more drivers head out on the red-banded rubber.

Not a strong opening sector for the Finn, while Hamilton posts a PB. In S2 the Finn goes quickest, but moments later the world champion goes quicker.

At the line Bottas posts 44.162 to go top, but Hamilton responds with a 43.840.

Cat lover Albon splits the Black Arrows with a 44.134, as Ocon goes quickest in S1.

Russell goes 9th with a 45.463 as Ocon posts 44.208 to go 5th.

Hamilton is told that all three tyres may well work this weekend.

A 43.744 sees Verstappen go top with former teammate Ricciardo going second (43.792) moments later.

Perez goes fifth (44.137) ahead of Bottas as the top six are covered by 0.418s.

Sainz goes ninth (44.474), as Leclerc can only manage 14th and Vettel 16th.

Indeed, as in FP1 and Alfa is quicker than the Ferraris, only this time around it is Giovinazzi.

"Work is progressing and the floors are being fitted to both cars," reports Haas, as Vettel complains of vibrations in his front tyres.

A mistake at T19 sees Bottas abort his next flying lap.

A 44.896 sees Raikkonen improve to 14th, ahead of Leclerc.

With 32:00 remaining, Magnussen finally heads out, the Dane paying tribute to his engineers. He moves straight on to softs.

Magnussen crosses the line at 46.242 to go 19th, as teammate Grosjean heads out. Both drivers missed all of the first session, and pretty much an hour of this one.

As the Haas pair continue they are joined by their rivals as the race sims get underway.

Perez is all over the rear of Hamilton, the Mexican nailing the world champion on the approach to Les Combes, courtesy of DRS.

Ricciardo slows on the Kemmel Straight, the Australian pulling over to the side of the track. As he tries to climb from the car, which isn't easy due to the steep incline, the VSC is deployed.

Replay shows he suddenly lost power. "Stop the car!" he is firmly told.

"What's wrong with the car Daniel," he is asked. "Err, I don't know," he replies.

Elsewhere, a bit of a moment for Hamilton as he exited the pits, the Mercedes getting worryingly out of shape after getting a little too eager when applying the power.

On their race sims Verstappen is looking strong, while Perez is matching Hamilton.

The session is red-flagged but it is unclear why.

Ah, "debris on track after Turn 1" reveals race control as the camera cuts to a piece of advertising hoarding on the track at the exit to La Source.

Renault reveals that Ricciardo suffered a loss of hydraulic pressure.

The session resumes with 10 minutes remaining however, the stoppage will have interrupted the flow at a critical time in the teams' programmes.

As the drivers head out again there is a mixture of all three compounds, though few are running the softs at this stage.

Albon is told he has time for four timed laps.

All drivers are on track bar Ricciardo.

"100% pace, 100% pace for two timed laps," Norris is told.

Under pressure from Hamilton, Vettel locks-up in T1, though based on today's pace is not something he will need to worry about on Sunday.

The session ends. Verstappen is quickest, ahead of Ricciardo, Hamilton, Albon, Perez, Bottas, Norris, Ocon, Sainz and Gasly.

Stroll is eleventh, ahead of Kvyat, Giovinazzi, Raikkonen, Leclerc, Russell, Vettel, Latifi, Grosjean and Magnussen.