Ahead of today's second free practice session the air temperature is 30 degrees C, while the track temperature is 33 degrees. Being that it is now 17:00 (local time) the temperature has dropped - and will continue to do so - consequently grip levels will have changed since this afternoon.
Lewis Hamilton was the pace-setter, the Englishman heading a McLaren 1-2, with Sebastian Vettel and Fernando Alonso third and fourth but both over 0.7s off the pace.
As the championship races towards its climax most teams are running new parts while some are testing new components for next season. In its eagerness to try some new parts that had just arrived from Maranello, Ferrari broke the official curfew for the first time this season.
With its back against the wall, Ferrari is bringing on new components at an alarming rate, Red Bull, clearly on a roll, also introducing updates but not at the same frantic pace.
Having given up their cars this morning, this afternoon Paul di Resta, Vitaly Petrov, Narain Karthikeyan and Charles Pic are in action. Unfortunately, Giedo van der Garde, who replaced Petrov in the Caterham, failed to post a time after suffering an engine problem.
Perez heads the queue at the end of the pitlane and when the lights go green he leads Kobayashi, Raikkonen, Vergne, Grosjean, Kovalainen and Pic on to the track.
Perez gets things underway with a 1:45.819 but this is soon beaten by the Lotus duo, Raikkonen going quickest with a 44.703. However, Vettel is clearly a man on a mission, the German, out unusually early, bangs in a 43.323 having gone quickest in all three sectors. Next time around he improves to 43.067.
Just seven minutes into the session, all twenty-four drivers are on track. The resultant traffic means lots of frustration, not least for Perez who gesticulates angrily at Schumacher.
Setting a frightening pace, Vettel improves to 42.779 the German displaying the same remorselessness we once saw from Schumacher.
Button, currently sixteenth, goes quickest in S1, and again in S2. At the line the McLaren driver posts 42.804, just 0.025s shy of Vettel. Webber goes third with a 43.366.
Currently seventeenth (46.843), Hamilton goes quickest in S2, subsequently crossing the line at 42.790, Vettel having raised the bar with a 42.730. The top three covered by 0.074s.
Alonso goes fourth but remains 0.337s off Vettel's pace, the Spaniard subsequently locking-up and thereby ruining his next lap.
An improvement from Hamilton (42.777) but he remains a tantalising 0.047s off Vettel's best.
Twenty minutes into the session there are only four drivers on track, Hamilton, who is told to "box" asks if he can a stay out a bit longer. Senna improves to thirteenth, the Brazilian one of several drivers yet to confirm a seat for next season.
As opposed to brake failure, HRT has now succumbed to a rear wing failure, de la Rosa the victim.
Hamilton, who has stayed out even longer than planned, goes quickest in the first two sectors, finally crossing the line at 42.095, eclipsing Vettel by 0.635s.
As Vergne switches to softs, the first driver to do so, Hamilton goes quickest in S1 before diving into the pits. Elsewhere, a big lock-up for Webber in T17.
The current order, after twenty-eight minutes, is: Hamilton, Button, Vettel, Alonso, Webber, Massa, Raikkonen, Senna, Schumacher and Rosberg.
Alonso is running the new front wing while Massa sticks with the old, the Spaniard clearly suffering oversteer. On the softs Vergne posts a disappointing 45.073.
Vettel splits the McLarens with a 42.622 as on board footage shows Maldonado really having to fight with the Williams. Cameras also pick up Webber running very low bringing back memories of Vettel late in last week's race.
At 51:15, Perez is the second driver to switch to softs as mechanics inspect the bottom of Webber's car.
Perez improves to twelfth with a 43.855 but like Vergne the improvement on the medium rubber is not especially significant. Rosberg is also on the option tyre now.