Ahead of today's opening session at Mexico City - as F1 returns following a 23 year hiatus, the air temperature is 18 degrees C, whilst the track temperature is 21 degrees.

Whilst the weather has been perfect up to now, a shower has left parts of the track damp. We are, of course, expecting heavy rain tomorrow.

Tyre options are the same as Austin - and no, we don't mean full wets and Inters - rather medium and soft. Indeed, the session is declared wet.

There are two DRS zones - though one detection point - the first activation point is on the pit straight and the second on the run between Turns 3 and 4.

"Dampest part of the track seems to be the pit lane," says Pirelli, "which is why mechanics are busy with hair dryers on the asphalt."

The lights go green and it is Pastor Maldonado who is first out, followed by Ericsson, Vettel, Verstappen, Nasr, Rossi and Raikkonen, All are on Inters.

Other than the damp, the brand new track asphalt will already be slippery.

Alonso is another early riser, the McLaren fitted with an aero rake. Indeed, a number of cars are running aero devices and the ubiquitous flo-vis.

A number of drivers appear to be caught out at T8, among them Alonso and Massa.

The sizeable crowd cheers as local hero Perez heads out.

"It's so slippery everywhere," complains Verstappen, the Dutch youngster confirming that it is not yet time for slicks, a view shared by Alonso, who says the "conditions are like ice, very strange".

Slow-mo shows ripples running through the car as Ricciardo rides the kerbs.

Raikkonen posts the first time of the day (37.169) but this is soon beaten by Verstappen (35.283) despite running wide in T11.

Having gone second (of three), Vettel lists the grip conditions of each corner, from memory, after just a couple of laps of running.

As Sainz goes quickest (33.095), Vettel says that it is too dry for Inters now. Kvyat goes second, ahead of Verstappen, Vettel, Bottas and Nasr.

As DRS is enabled, Rosberg goes second with a 33.174.

Twenty minutes in, the Williams duo is first to switch to slicks (medium), along with Vettel.

Bottas goes quickest in S1, but it is Verstappen (Inters) who is quickest in S2. At the line Bottas posts 32.489 to go quickest, 0.606s quicker than Sainz. Next time around the Finn improves to 31.868.

"I don't know why but I have nothing at the rear," complains Raikkonen, before adding "rear grip". Meanwhile, teammate Vettel, on the primes, goes second with a 32.151.

Rosberg runs wide in T6 and Hamilton at T4, though the Briton goes on to post 31.160 and take second.

The opening half hour comes to an end - when the 'free' set of tyres is handed back - and currently Bottas leads the way, ahead of Hamilton, Perez, Nasr, Vettel, Massa, Raikkonen, Sainz, Rosberg and Verstappen.

After a brief break, Kvyat heads out again, the Russian on a new set of the prime rubber.

Mechanics swarm over Raikkonen's car, the Finn appearing to have a brake issue.

Kvyat improves to third with a 31.643, whilst teammate Ricciardo can only manage 33.824. Shortly after however, the Australian improves to fourth with a 31.862 before going quickest with a 30.577.

On-board footage of Ricciardo shows the car to be a real handful.

From out of nowhere Maldonado posts 30.272 to go second however,. Moments later he is leapfrogged by Alonso (30.125).

Despite a scrappy lap, Hamilton improves to fourth with a 30.126. Moments later however, Palmer posts 29.163 to take the top spot for the first time this year.

Slowly the track is coming to the drivers, as proven when Rosberg bangs in a 28.399.

Having improved to second (28.744), Verstappen looks set to improve again but fails indeed, he slips to third when Perez posts 28.573.

New circuit but same old scene as Hamilton goes second to Mercedes teammate Rosberg.