Ahead of today's second session, the air temperature is 23.1 degrees C, while the track temperature is 39.3 degrees. It remains bright and sunny.
Sebastian Vettel set the pace in FP1, the Ferrari pair out-pacing the Red Bull and Mercedes.
That said, despite a scrappy session for Lewis Hamilton, both Mercedes drivers posted their best times on the medium rubber.
Lance Stroll was best of the rest, ahead of Ricciardo, Perez and Sainz.
The lights go green, and Grosjean leads the way, followed by his Haas teammate. They are followed by the Williams pair, Russell back in the car after handing over to Nicholas Latifi earlier.
Magnussen posts 48.560, Grosjean 49.031 and Russell 53.928.
This morning's pace-setter is keen to get back to work, the German subsequently posting a 46.069 on the mediums.
Leclerc responds with a 45.377, as Perez and Stroll go third and fourth for Racing Point.
Both Ferraris quicker than the Mercedes pair were on the mediums earlier, albeit in warmer conditions.
Other than the Williams pair, where Russell is on hards and Kubica softs, everyone is on the yellow-banded medium tyre.
A 46.849 sees Giovinazzi go fourth, ahead of Norris and Sainz.
Renault is to carry out its long run with high fuel, with both drivers running identical programmes. Seemingly, the French team doesn't believe the hards are much good here and will not be "wasting" time using them today.
A 45.621 sees Hamilton go second, with teammate Bottas posting 45.781 moments later.
Twenty-three minutes into the session, Verstappen finally emerges, much to the relief of his many thousands of fans, subsequently posting a 45.394 to go second.
As the McLaren pair try some slipstreaming, Hamilton pits after complaining about dust and dirt getting inside his helmet due to a loose visor.
Verstappen warns that he "heard something" under braking for the Bus Stop. He subsequently claims that he is "losing power".
Half-an-hour in and Vettel is among the first to make the switch to softs, the Haas pair follow suit.
Quickest in the first two sectors, Vettel goes quickest (44.753), despite a poor final sector.
Grosjean goes sixth (4.120) and Magnussen eighth (46.399).
Bottas, now on softs, goes second with a 44.969, ahead of Perez. Moments later, Hamilton crosses the line at 45.015 to go third.
Quickest in the first and final sectors, Leclerc goes top with a 44.123, 0.630s quicker than his teammate.
A potty-mouth call from Mr Raikkonen as he complains about traffic... on the longest track on the calendar.
Verstappen switches to the softs, however, a weak opening sector is followed by a PB. Another poor final sector sees the Red Bull driver fail to improve on sixth (45.394).
In a bid to cool their overheating tyres a number of drivers are opting for double cool-down laps. However, the additional mileage compromises their chances of improving their times.
As ever, focus switches to Sunday and the opening stint as the drivers get stuck into their high-fuel long runs.
Magnussen waits patiently in his car as mechanics work on it, the cause of his issue unclear.
"There's something burning like crazy in the back of my seat," warns Stroll, "I can smell burning too". The Canadian subsequently pits, but despite his radio calls appears in no rush to vacate his seat.
"I think I have the same thing again, engine braking doesn't feel right," says Verstappen, clearly referring to ongoing power issues. He too pits, albeit for a switch to mediums.
Back on track, Stroll is still happy and complains that something is burning. He is told that if it continues he may need to pit and have his seat removed.
And as if by magic, Stroll's teammate Perez stops on track with smoke billowing from his car and even a few flames.
The VSC is deployed.
The Mexican, who is currently fifth, is clearly not happy.
The session is eventually red flagged, with less than two minutes remaining.
On long run pace, Mercedes has the edge, with Verstappen not far behind, but ahead of the Ferraris. However, with no data on fuel loads, we shouldn't read too much into that.
As in FP1, Ferrari leads the way, though this time around it is Leclerc who is the pace-setter.
Vettel is second, ahead of Bottas, Hamilton, Perez, Verstappen, Raikkonen, Stroll, Ricciardo and Albon.
Sainz is eleventh, ahead of Grosjean, Hulkenberg, Kvyat, Norris, Giovinazzi, Gasly, Magnussen, Russell and Kubica.
Check out our Friday gallery from Spa, here.