Ahead of today's second session the air temperature is 29 degrees C, while the track temperature is 40 degrees. Humidity has dropped to 72%.
Max Verstappen led a Red Bull 1-2 in this morning's session, ahead of Alonso, the Ferraris and Mercedes.
However, other than the fact that the session was reduced to one hour due to heavy rain at the start, it was pretty much redundant anyway because it takes place at an earlier time than any other session.
Furthermore, an already truncated session saw even less running due to the fact that further rain is expected over the rest of the weekend and drivers have a limited number of rain tyres.
Felipe Massa was the only driver who failed to post a time, the Brazilian sidelined by a hydraulics issue.
With a number of third and reserve drivers on duty earlier, this session sees Hulkenberg, Ericsson, Magnussen and Sainz get their first taste of Sepang 2017.
The lights go green and Wehrlein leads the way, followed by teammate Ericsson and Sainz.
An early complaint form Raikkonen who is concerned at a vibration from his tyres.
Having lost so much time earlier, this afternoon the drivers are clearly keen to make up lost time. Just a couple of minutes into the session we already have seven names on the board with Raikkonen (33.486) leading the way.
Most are on softs, though the Toro Rossos are on mediums and Williams and Alonso on supersofts.
Palmer complains of oversteer off the brakes at low speed.
While Raikkonen improves to 32.836, Verstappen is clearly on a hot lap and subsequently takes the top spot with a 32.739.
A baptism by fire literally for Gasly whose Toro Rosso spouts flames and smoke as he enters the pits.
Massa's first timed lap of the day sees the Williams driver go sixth with a 33.893.
Vettel improves to second while Ricciardo consolidates fourth with a 32.977.
Another improvement sees Vettel take the top spot (32.566), as Hamilton can only manage fifth (33.228).
No sooner has he locked up in the final corner causing him to have to cut across the pitlane entry than Palmer warns: "Front locking becoming a problem". Indeed it is.
Out come the yellows as Bottas goes off at T11. The Finn takes a long drive on the grass that surrounds the gravel trap having enjoyed a trip through said gravel. He heads back to the garage to check for damage.
"It's horrible, absolutely horrible," complains Sainz, "the driveability, entry... everything", as Stroll runs wide in T8.
Now it's Hamilton's turn to have an issue, the Briton spinning and sliding off the edge of the track and across the gravel, much to the consternation of Toto Wolff who is still recovering from Bottas' scare. Like his teammate, Hamilton heads for 'home'.
Sainz is the latest driver to go off, though unlike the Mercedes duo he merely dips a wheel into the gravel. Nonetheless, slow-mo TV replay shows the Toro Rosso taking a pounding.
"Undriveable, this thing is giving me so much oversteer," he complains. "Like a handbrake, I nearly spun because of it."
On the supers, Hulkenberg posts 33.069 to go 5th.
Also on the supers, Ricciardo goes quickest in S1. He maintains the pace in S2 as teammate Verstappen begins his first lap on the red-banded rubber. At the line Ricciardo posts 32.099 but a poor final sector means his teammate fails to improve.
With the Mercedes duo still in their garages following their (mis)adventures, the Ferrari duo head out on the supersofts.
Alonso improves to 10th with a 33.665.
Unsurprisingly, Vettel goes quickest in S1. However, Raikkonen has the edge in S2. At the line the Finn posts 31.865 only to be beaten down to second when Vettel slips in a 31.261.
Stroll demolishes the bollard at the pitlane entrance after making a hash of the final corner. "I have problems with the brakes," says the Canadian, "and I've flat-spotted the tyres.
"I hit the bollard by accident too," he adds.
Elsewhere, an excursion for Ericsson who is off at T9.
"The understeer on this thing is crazy," complains Magnussen. "Yes, we've had the same comment from Romain" he is told. We wonder which driver used the most expletives however.
Another unusual incident as the cameras pick up on a ventilator falling from Massa's helmet.
Hamilton improves to fifth with a 32.677 but is a scrappy lap and the time hard fought, the Mercedes clearly suffering major understeer. He is 1.416s off Vettel's pace.
It goes from bad to worse as Alonso posts 32.564 to leapfrog the Mercedes duo and take 5th.
Ferrari apologises to Raikkonen after a piece of black gaffa tape was left on his tyre and subsequently found its way to his suspension. "Sorry about that Kimi, we knew we were going out with the tape. We thought it would come off, we didn't realise it was on the suspension too until the last minute."
With 25 minutes remaining, attention, as ever, switches to the opening phase of Sunday's race as driver begin their simulations.
"For info, degradation on supersoft looks quite low," Ricciardo is told.
Sainz complains that he has no power on the straight. He is told to pit immediately. Well, in fact he is told to "box, box, box, box!"
The session is red flagged when Grosjean goes off and into the barriers at high speed at T13. The medical car is immediately deployed but the Frenchman is already out of his car.
It was a big, big impact, the Haas going off and skating into the barriers backwards after his right-rear tyre was shredded by a loose drain cover. The drain cover appeared to come loose after Raikkonen ran over it.
A nasty incident and one which will have repercussions.
Ferrari reveals that Raikkonen had previously warned: "There is something sticking out of the kerb". Indeed, it appears the cover was actually dislodged by countryman Bottas.
With 12:40 remaining and the drain cover needing to be repaired, it is unlikely that there will be any further running.
Charlie Whiting is among those checking the drain cover... or rather the exposed drain.
With 9:08 remaining, it is confirmed that the session will not re-start.
Consequently, Vettel remains quickest, ahead of Raikkonen, Ricciardo, Verstappen, Alonso, Hamilton, Bottas, Perez, Hulkenberg and Ocon.
Palmer is eleventh, ahead of Massa, Vandoorne, Stroll, Gasly, Sainz, Grosjean, Magnussen, Wehrlein and Ericsson.
Check out our Friday gallery from Sepang, here.