Ahead of today's qualifying session the air temperature is 36 degrees C, while the track temperature is 43 degrees.
Max Verstappen set the pace in practice, while Leclerc, Hamilton, Perez and Magnussen rounded out the top five.
Neither McLaren or Aston Martin drivers tried the softs, with Stroll sitting out much of the session doe to a brake issue.
Mercedes, like Haas, has a significant upgrade package this weekend, and both appear to be benefitting, while AlphaTauri has yet to show what its upgrades can do.
At Mercedes and Ferrari only one driver appeared to look totally in control, with the German team admitting that Russell might have gone the wrong way in terms of set-up.
Though we have had just the one session, McLaren appears to be struggling - as Lando Norris had suggested it might - while a number of drivers have complained about the bumps and the overall lack of grip.
While the track limits were not officially policed earlier there was a sizeable number of violations, and this could prove to be an issue over the remaining sessions.
The lights go green and Sargeant leads the way, followed by Gasly, Zhou, Bottas and Ocon.
As Sargeant pits, Gasly posts the first time of the afternoon, the Frenchman crossing the line at 37.529. However, Bottas responds with a 36.843 and Norris a 36.640.
A 36.622 sees Leclerc go top as Piastri goes third with a 36.831.
Perez stops the clock at 36.680 to go third, 0.058s off Leclerc's pace.
Alonso goes sixth with a 37.032 but is demoted when Verstappen stops the clock at 36.470.
Running wide in T19, Hamilton can only manage fifth (36.742). He is subsequently demoted when his teammate goes third with a 36.625.
As Stroll pits for a change of tyres, great clouds of brake dust billow from all four corners of the car.
Hulkenberg goes quickest with a 36.235 as his teammate posts a 37.138 to go fourteenth.
Gasly goes quickest (36.158) as Tsunoda goes 13th and Ricciardo 17th.
Sargeant and Zhou both have times deleted for track limits violations.
Despite that brake dust Stroll goes sixth with a 36.624.
Sainz goes quickest in S1 as the Spaniard seeks to improve on 18th. No sooner has his teammate gone quickest (36.119), than Sainz crosses the line at 35.824.
Despite a lot of traffic Verstappen goes quickest in S1. He only manages a PB in S2, finally crossing the line at 35.346 to go top by 0.478s.
Perez improves to third with a 35.989 as Hamilton goes quickest in S2.
Hamilton goes quickest with a 35.091, as Albon goes 8th, Russell seventh and Norris second.
Hulkenberg goes tenth, Zhou sixth and Leclerc eighth.
Magnussen goes sixth and Bottas tenth, while Tsunoda goes fifth.
Ocon goes twelfth while Alonso can only manage 17th.
Quickest is Hamilton, ahead of Norris, Verstappen, Sainz, Tsunoda, Perez, Magnussen, Zhou, Leclerc and Piastri.
We lose Hulkenberg, Alonso, Albon, Stroll and Sargeant. That's the first time this season that Alonso hasn't made it out of Q1.
Leclerc is first out for Q2, followed by his Ferrari teammate. Hamilton is next out, followed by Russell and Norris.
Stroll and the AlphaTauri pair will be investigated after the session for failing to adhere to the minimum time rule.
Hamilton goes quickest, but is demoted by his teammate who crosses the line at 35.759. However, Russell is on fresh rubber and Hamilton on used.
No sooner has Norris gone second than his time is deleted.
Verstappen goes quickest with a 35.491 and Piastri second.
Gasly goes third, ahead of Russell, Hamilton, Tsunoda and Leclerc, but all are demoted when Ocon posts a 35.600 to go third.
"Tsunoda didn't get out of the way in Turn 15, he pushed me wide," complains Sainz.
Leclerc is concerned that his time has been deleted but he is assured that it hasn't.
Leclerc is first out for the final assault, followed by his Ferrari teammate.
Leclerc goes quickest in S1, but Sainz goes quicker. In S2 the Monegasque has the edge but Verstappen is also on a hot lap.
Leclerc goes quickest with a 35.004 while Sainz responds with a 35.302.
A 35.008 sees Verstappen go second, 0.004s down on Leclerc.
Norris goes fourth as Hamilton goes quickest in S1.
Zhou goes ninth but is leapfrogged by Tsunoda.
Gasly goes fifth as Ricciardo has his time deleted.
Hamilton goes third (35.420) following a wobble in the final corner, while Russell claims ninth by the skin of his teeth, likewise Perez.
Quickest is Leclerc, ahead of Verstappen, Hamilton, Sainz, Ocon, Norris, Gasly, Piastri, Russell and Perez.
We lose Tsunoda, Zhou, Bottas, Magnussen and Ricciardo.
Check out our Friday gallery from COTA here.
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