Ahead of today's second practice session the air temperature is 16 degrees C, while the track temperature is 35 degrees. It is still cooler but better than this morning.
Lewis Hamilton set the pace in this morning's session - as he so often does - with the Ferrari duo second and third. Nico Rosberg was a distant seventh 0.795s off the pace but we shouldn't read too much into that.
What we should into is the fact that the track is very dusty and grip is not helped by the cool temperatures either. Furthermore, the use of all three compounds gave us little opportunity to do any meaningful comparisons.
For example, Hamilton's best time was set on the medium, while the Ferraris were on softs and the Force Indias in fourth and fifth on supersofts... a real mixture.
A number of drivers also suffered brake issues, most notably Max Verstappen, Christian Horner subsequently claiming that they were "out of control".
The Briton puts this down to the thinner air, Mexico City being at such a high altitude, a geographical factor that also effects aerodynamics and the engines.
To further liven things up the session was red flagged when Felipe Nasr's front wing disintegrated and at the very end of the session there was a brief rain shower at T3.
The lights go green and as in FP1 Grosjean leads the way, followed by Wehrlein and Raikkonen.
As Wehrlein posts 32.162, Grosjean is advised he has a problem and is told to pit. Having made a mistake at T13, the Frenchman is told his shifting is OK.
Raikkonen posts 27.665 with teammate Vettel posting 27.974 moments later.
The softs improving on the second lap, Wehrlein crosses the line at 22.909 to go quickest.
Like Wehrlein, Raikkonen improves on his second lap, stopping the clock at 22.075. Despite being quickest in S1, Vettel can only manage 22.951.
Eight minutes in and Rosberg heads out, leaving his teammate, Ricciardo, Bottas and Button as the only no-shows.
Vettel ups the ante with a 22.024 as local hero - but not THE local hero - Gutierrez posts 22.668 to go third.
A big, big moment for Verstappen but he keeps it all perfectly under control. Elsewhere, a brief spin for Perez at T5 and Rosberg runs wide in T1 following a big lock-up.
Asked if he incurred any damage Perez replies: "It's very loose".
In the meantime, Alonso has gone third with a 22.106.
Rosberg's first timed lap is a 29.666 while Hamilton posts 31.849. However, next time around the Briton goes quickest in all three sectors, finally crossing the line at 20.362.
"Really different than before," says Massa. "Oversteer, going sideways pretty easy in the corners."
Ericsson spins at T11 as drivers continue to struggle.
From out of nowhere, Sainz (softs) produces a 21.896 to go second. Nonetheless, he is 1.534s off Hamilton's pace.
Rosberg improves to fourth (22.041) as Grosjean's day appears to be at an end, the team understood to be needing a possible hybrid change.
As he disappears in a cloud of tyre smoke, Hamilton warns: "This tyre is completely done guys."
Similar problems for Jenson Button aka Capt. No Grip, who confirms, not for the first time, that he is struggling. "The rear feels like it's just falling over, big snaps all the time," he says.
"I have a lot of oversteer," says Bottas, his voice trembling with the vibration, "especially right-hand corners."
Vettel is the first driver to switch to the supersofts, as Rosberg, on mediums, improves to second albeit 1.054s off his teammate's pace.
On his second flying lap on the supers, having aborted the first, Vettel goes quickest. He maintains the pace in S2, finally crossing the line at 19.790.
Consequently, Vettel now tops the timesheets on supers, ahead of Hamilton (softs) and Rosberg (mediums).
Now Raikkonen switches to the red-banded rubber, what can the Finn do?
Vettel pits but his crew is unprepared so he heads out again.
Raikkonen can only manage PBs in the first two sectors, finally crossing the line at 20.259, 0.469s down on his teammate.
More drivers now switch to the supersofts, most notably the Mercedes duo.
Among the first to improve is Kvyat who goes fourth (21.286), while Magnussen posts 21.442 to go sixth.
Rosberg can only manage fourth (20.406) having had a poor S3 after running wide in T12. Indeed, he was only quickest in S2.
Hamilton, as expected, goes quickest in S1, though he loses a little pace in the second sector. At the line he posts 19.803, to go second 0.013s off Vettel's best.
"I've got a lot of traffic, it's going to destroy my lap," warns Massa as he posts 21.326 to go 11th.
Gutierrez locks-up and runs wide in T1.
As Hamilton complains of traffic, Hamilton is told that the team wants to get on with "the programme". He responds by going quickest in S2, finally crossing the line just 0.004s off Vettel's time.
At halftime, it's: Vettel, Hamilton, Rosberg, Raikkonen, Ricciardo, Hulkenberg, Verstappen, Bottas, Sainz and Kvyat.
Check out our Friday gallery from Mexico City, here.
Alonso improves to tenth and Button twelfth, the pair mixing it with the Toro Rossos.
Sainz gets a lovely tow from Magnussen as Pirelli says: "particularly strong pace from Hulkenberg, 6th fastest using soft tyre, highest placed soft tyre runner".
Unhappy at the way Magnussen attempted to resist him when he passed, Sainz says of Magnussen: "This guy has no brains!"
Attention has now switched to Sunday as drivers begin their longer runs on heavy fuel.
Having both performed practice starts Hamilton says his was "very good" while Rosberg complains his was "under engaged" and wants another go.
As he complains of big degradations front and rear Rosberg is told to stay out. He complains of heavy traffic but is told to find a gap and stay out.
The German is not alone, more and more drivers complain of degradation to their supersofts.
Meanwhile, Grosjean is back on track with 22:00 minutes remaining.
Traffic is clearly an issue with Hulkenberg and Vettel among the many drivers complaining, however this is hardly Monaco.
Vettel runs wide after a misunderstanding with Alonso, for some strange reason the German isn't happy. Then again neither is Alonso. Neither has a good word to say about the other, well in fact they do, but that word is not repeatable.
Wehrlein complains of an issue with his engine which is causing "big snaps of oversteer".
Alonso is out of his car and walking through the paddock, his day's word seemingly done. Yet he appears quite happy.
"I'd rather do the starts then keep driving around," says Raikkonen, "we're learning nothing but I can continue to keep driving around if that's what you want."
What can you say?
Some pace info would be nice," says Hulkenberg as the drivers appear a little more tetchy than usual.
With nine minutes remaining, there's still a real mixture of compounds, the 21 drivers on track using all three. That said, most are on mediums with just Hamilton, Sainz and Wehrlein on the softs.
Told he can use DRS to stay ahead of a slower car, Magnussen responds: "There's no point," his tyres clearly shot.
Verstappen and Kvyat are the latest drivers to have little differences of opinion with their engineers. The Russian argues when told to watch out for Sainz who is behind. "You should have kept pushing, I didn't tell you to let him by," he is told. "Too late man," he replies.
And then there's Vettel, "This is just silly, people using DRS to defend, what are we going to learn here, nothing," he moans.
Kvyat has pulled to the side of the track just before the pitlane entrance. "Switch the car off as soon as you can," he is told as smoke pours from the car.
Rosberg is told quite firmly to watch the yellows as he enters the pits following Kvyat's stoppage.
So, in a session that was more about driver tetchiness than grip, spins and lock-ups, Vettel is quickest - and when was the last time you read that - ahead of Hamilton, Rosberg, Raikkonen, Ricciardo, Hulkenberg, Verstappen, Bottas, Sainz and Alonso.
Kvyat is eleventh, ahead of Button, Massa, Magnussen, Perez, Palmer, Wehrlein, Ericsson, Nasr, Grosjean, Ocon and Gutierrez.
Check out our Friday gallery from Mexico City, here.