Ahead of Q1, the air temperature is 29.2 degrees C, while the track temperature is 41.6 degrees.
With Ferrari having set the pace in all three practice sessions, the question on everyone's lips, other than which of the Scarlet clad drivers might take pole, was what Mercedes might have up its sleeve.
With the German team introducing an upgraded power unit this weekend, many were wondering if the infamous 'party mode' might now go up to 12.
However, Lewis Hamilton's crash late this morning changed all that, and right now the big question is will the Briton even take part.
Mercedes is confident that he will, revealing that it "will be replacing both front corners (suspension and wheel assemblies), nose, barge boards and floor".
However, it carefully adds: "Barring any unexpected surprises, we believe we can complete all of the work in time for the start of qualifying."
Hamilton's crash follows an unusually scrappy Friday, causing one to wonder whether the world champion is having one of those 'off' weekends he has from time to time.
That said, he'll probably go out and take pole by over a second... he's that kind of guy.
While Ferrari clearly has the outright pace, on the long runs yesterday it was losing out to both Mercedes and Red Bull.
Though Max Verstappen is playing down his chances, clearly keen to put the power circuits, like Spa and Monza, behind him, the Dutchman must never be written off, especially, if as predicted, temperatures drop tomorrow.
Whatever happens over the next hour, courtesy of numerous grid penalties how they finish today is not how they will start tomorrow. Meanwhile, to further confuse the issue, having taken on new units - and thereby taken the resultant penalties - the Renault pair and Carlos Sainz have reverted to their old engines. Likewise Carlos Sainz, whose new-spec Mercedes engine suffered a failure in FP2.
While the penalties will help juggle up the grid tomorrow, the Alfas have looked strong this weekend, both drivers benefiting from an upgraded Ferrari engine which the works team won't use until next week. Unfortunately, the Haas pair are not showing a similar step forward.
As will be the case at Monza next week, a number of teams are sure to try to benefit from slipstreaming, Sebastian Vettel's best lap this morning coming courtesy of a two from his teammate through Blanchimont.
Ten minutes before the start of the session, the screens are removed from the front of Hamilton's garage, mechanics still working frantically on the silver car.
Another factor worth considering is that drivers have been warned about the track limits, in particular at Raidillon. Any driver leaving the track and cutting behind the apex will have their time disallowed. Though the rule has been in force all weekend, it is in this session, and again tomorrow, when drivers take the extra risk and push that little harder.
The lights go green and Russell leads the way, followed by teammate Kubica.
As more drivers head out, Kubica suffers a dramatic engine failure, echoing that of Perez yesterday, both of whom have the latest-spec unit, as do the Silver Arrows drivers. As was the case yesterday, flames and smoke erupt from the stricken unit.
The session is red flagged.
At the time of the red flag there were 18 drivers on track, Hamilton and Kvyat still in their garages.
While this gives the Mercedes crew more time to work on Hamilton's car, back-to-back engine failures for customer teams must cause the German manufacturer some serious concern.
Meanwhile, there is clearly something happening in Leclerc's garage, there are a number of crew members blocking the view, while an FIA official is looking at the front of the car. No such issues in the neighbouring garage of Vettel.
As the session resumes, with 12:59 remaining, Verstappen heads a long queue of drivers keen to get back to work. Among them, Lewis Hamilton.
As Verstappen heads out, he is cheered on by the crowd.
"Small vibration in the front tyres," reports Hamilton.
"Problem, problem," reports Verstappen as he aborts the lap, crossing the line at 51.843.
The screen lights up (finally for app users), as the times tumble. Hamilton goes top (45.260), then Bottas (45.141), then Leclerc (43.587). Vettel goes second with a 44.109, 0.522s down on his teammate.
Albon goes fifth, best of the rest, ahead of Ricciardo, Giovinazzi, Grosjean, Perez and Magnussen.
The initial runs completed, while Kubica and Verstappen haven't posted times, Russell, Kvyat and Sainz are all in the drop zone, with Gasly, Norris and Stroll hovering.
The Mercedes pair remain out on track, both posting PBs in various sectors.
Verstappen heads out again, with just over three minutes remaining.
Despite the traffic, nobody impedes the Dutchman, who crosses the line at 44.622 to go third.
Moments later the session is red flagged when Giovinazzi grinds to a halt on the pit straight with smoke billowing from the rear of his car. "Issue, issue," reports the Italian.
A few seconds earlier and Verstappen wouldn't have qualified.
As a result, Gasly, Sainz, Kvyat and the Williams pair fail to make the cut.
Leclerc is quickest, ahead of Vettel, Verstappen, Bottas, Hamilton, Albon, Ricciardo, Giovinazzi, Grosjean and Perez.
While Sainz accept his fate calmly, not so Kvyat who utters a stream of expletives.
After a short delay, Q2 gets underway, and Albon is first out, followed by the Haas duo and Raikkonen.
As more drivers head out, including the Mercedes and Ferrari pairs, all are on softs.
Raikkonen posts 44.140, while Albon can only manage 45.799.
Ricciardo goes second with a 44.632, ahead of Perez and Stroll.
A 43.592 sees Hamilton go top, with Leclerc leapfrogging him with a 43.376 moments later.
Despite going quickest in S1, Vettel can only manage PBs in the final sectors, posting 43.506 to go second.
Bottas goes fourth (43.980) and Verstappen fifth (44.132).
Impressive performance from Raikkonen who is only marginally off Verstappen's time... in fact, eight-thousandths.
Hulkenberg, Grosjean, Norris, Albon and Giovinazzi comprise the drop zone.
Ahead of the final runs, Albon is out of his car, he clearly won't be running again.
The Haas pair head out nose-to-tail, which, all things considered, must constitute a recipe for potential disaster.
Hulkenberg is told that he's tenth, but in fact he's eleventh. Hope Renault isn't relying on the Timing App.
Like his teammate, but for different reasons, Verstappen opts not to run again.
Hulkenberg looks set to improve, as do Grosjean and Norris.
Leclerc goes quickest in S1 as Hulkenberg improves to seventh.
Ricciardo goes fifth, while Norris fails to make the cut.
Bottas consolidates his fourth with a 43.980.
Leclerc raises the bar with a 42.938, with Vettel just 0.099s behind.
Quickest is Leclerc, ahead of Vettel, Hamilton, Bottas, Ricciardo, Verstappen, Raikkonen, Hulkenberg, Perez and Magnussen.
We lose Grosjean, Norris, Stroll, Albon and Giovinazzi.
Check out our Saturday gallery from Spa, here.