Ahead of today's opening session the air temperature is 29 degrees C while the track temperature is 36 degrees. Humidity is 71%.
There has been some rain so the track will be a little slippery at first. There is a 20% chance of further rain over the next hour, with further rain expected throughout the weekend.
As ever, due to the change of conditions for qualifying and the race, this session, like FP3, is somewhat unrepresentative.
In terms of updates, only two teams have them.
Red Bull has a new Front Wing and Engine Cover. The front wing is an evolution of the design taking further research to increase the camber of some wing sections to extract more load whilst maintaining flow stability, while the enlarged exit from the overall top body is more efficient than opening louvres or creating larger louvres to raise the overall cooling capacity.
Mercedes has a new Front Wing which has been reprofiled and drops the local load to allow an appropriate car balance to be achieved for this circuit.
As previously reported, this weekend is designated a heat event which means drivers have a special cooling vest available though it isn't mandatory.
The pitlane opens and Lawson leads the way, followed by Hulkenberg, Bearman, Ocon and Hadjar. As more drivers emerge the hards are very much the order of the day.
As ever, the Aston pair are the exception, both Stroll and Alonso opting for mediums. Though in all likelihood they are merely scrubbing them.
Of the first wave Piastri is quickest (36.253), but Hamilton responds with a 35.520 and Verstappen a 35.501.
Drama in the pitlane where smoke is billowing from Albon's Williams, its rear brakes seemingly ablaze. The mechanics start to push the car into the garage before having second thoughts.
A 34.329 sees Hadjar go top as Stroll goes tenth on his mediums and Alonso 18th.
Verstappen retakes the top spot with a 34.059 but is immediately leapfrogged by Hamilton (33.927).
Sainz is fourth, ahead of Piastri, Lawson and Tsunoda.
Smoke continues to billow from Albon's car.
Norris goes top with a 33.388 as Alonso improves to second with a 33.608.
Fresh from his Baku podium, Sainz goes top with a 33.325 but is immediately demoted by Piastri who stops the clock at 33.239.
Quickest in all three sectors, Alonso posts a 32.592.
Leclerc goes third, ahead of Piastri, Norris and Hamilton.
Williams confirms that the issue on Albon's car was not brake-by-wire but the brakes themselves. The team is confident he will take part in FP2.
Norris goes top with as 32.493 as Hamilton takes avoiding action after coming across a slow Red Bull and Gasly takes advantage of an escape road.
Verstappen goes second with a 32.514, 0.021s off Norris' pace.
Hadjar goes third with a 32.550.
At around half-time, Sainz is the first - other than the Astons - to switch to the mediums. Antonelli follows suit.
Alonso retakes the top spot with a 32.054 but is immediately demoted by countryman Sainz (31.812).
Stroll switches to the softs as Antonelli goes sixth (32.592) on the yellow-banded rubber.
Norris, Leclerc, Verstappen and Bearman witch to the softs.
Antonelli's lap is over before it has begun, the Mercedes driver suffering a big snap of oversteer in Turn 1.
Leclerc goes quickest in S1, maintaining the pace in the second sector. At the line it's 31.266, but Norris is on a strong lap.
Hadjar goes fourth, but is demoted when Verstappen goes third and then Norris second (31.698).
Piastri can only manage sixth, 1.045s off the pace, while Hulkenberg goes eighth.
"That felt very understeery," reports Piastri.
Both McLaren drivers pit for tweaks to their front wings.
Leclerc goes top with a 31.266, 0.432s up on Norris, as Verstappen takes second with a 31.392.
"Ferrari will invent mirrors one day, I hope," says Piastri after encountering a slow Hamilton.
The Australian subsequently improves to third with a 31.481, 0.215s off the pace.
On fresh softs Alonso goes quickest with a 31.116 as Piastri clips the barriers.
Williams and Mercedes have yet to run the red-banded rubber.
Hamilton improves to fourth with a 31.480.
"What the **** is he doing?" asks Bortoleto of the McLaren ahead.
Alonso tops the timesheets while his teammate is 18th.
As the high fuel runs continue all three compounds are in use.
"It's not very clever," says Sainz as he is forced wide by Hulkenberg who appears to think it's Sunday.
The session ends. Alonso is quickest, ahead of Leclerc, Verstappen, Hamilton, Piastri, Norris, Hadjar, Sainz, Tsunoda and Ocon.
Russell is eleventh, ahead of Hulkenberg, Gasly, Antonelli, Lawson, Bearman , Bortoleto, Stroll and Colapinto.
Check out our Friday gallery from Marina Bay here.
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