Ahead of this afternoon's sole free practice session, the air temperature is 31 degrees C, while the track temperature is 46 degrees. It is bright and sunny, with the humidity currently running at 50 percent.

Lewis Hamilton topped the timesheets in both of yesterday's sessions, while teammate Jenson Button and the Mercedes of Nico Rosberg and Michael Schumacher were well on the pace.

Mark Webber missed most of the second session as a result of an engine problem, while teammate Sebastian Vettel admitted that he wasn't "100 percent happy", claiming that the McLarens and Ferraris have "decent long run pace".

The Italian team concentrated on longer runs yesterday, however, its late low fuel runs were off the pace. Also off the pace was the Williams duo, while Renault, particularly Robert Kubica, Toro Rosso and Force India continue to make progress.

With today's action taking place three hours later than yesterday, much of the attention will be focussed on the weather, with Monsoon-type storms hitting the area like clockwork every day round about 17.00 for the last week.

The light go green and the Lotus duo of Trulli and Kovalainen lead the way, closely followed by Buemi, Chandhok, de la Rosa, Alguersuari, Vettel, di Grass and various others. They all complete the obligatory installation lap and head back to the pits.

Five minutes into the session all but the McLarens and Mercedes have made an appearance. That said, Hamilton, Button and Schumacher finally take to the track, leaving Rosberg as the only no-show.

Ten minutes into the session, as de la Rosa waits at the end of the pitlane, his engineer informs him that "rain is a few kilometres away", advising the Spaniard to "get on with it".

As de la Rosa begins his first flying lap he is joined by di Grassi, Liuzzi and Webber.

The Spaniard crosses the line at 1:36.891, but moments later Webber posts 34.920. The Red Bull looks superb, but that question mark regarding its reliability remains.

Next time around a slow final sector means the Australian fails to improve while Liuzzi goes second ahead of de la Rosa, Kobayashi and di Grassi.

Vettel crosses the line at 34.714 to make it a Red Bull 1-2, as Massa goes third only to be demoted when Ferrari teammate Alonso goes quickest with a 34.678.

The McLarens leave the pits, followed by Schumacher, while Rosberg is still to make an appearance.

Alonso consolidates his top spot with 34.514 as Liuzzi improves to fifth. Elsewhere, Rosberg heads down the pitlane.

On his first flying lap, Hamilton goes second with a 34.598, just 0.084s off Alonso's pace, while Button posts 35.128 to go fifth.

A 34.711 sees Schumacher go third while Mercedes teammate posts 48.991. All but Sutil have posted a time, the Force India not yet having reappeared following his installation lap.

Hamilton goes quickest in the final two sectors to go quickest with a 34.029 as Rosberg improves to sixth with 35.102. The usual suspects now fill the first eight places.

Petrov, who is wearing a black armband in honour of the victims of the Moscow subway atrocity, runs wide and goes cross country.

"Rain is due in five minutes," Button is told, as Sutil goes tenth with a 35.306. Barrichello posts 35.671 to go eleventh.

With an eye on the gathering clouds Hamilton leaves the pits to join his McLaren teammate, both are on the option (soft) tyre. Sutil posts 35.029 to move up to seventh, exactly one second off Hamilton's pace.

Hamilton goes quickest in the first sector, and again in the second, while teammate Button is almost 0.2s slower. At the line Hamilton posts 33.559 while Button makes it a McLaren 1-2 with a 34.113.

Buemi, also on the option, improves to fourth with a 34.673, as Alonso (soft) heads down the pitlane. With twenty-three minutes remaining, Barrichello is told that the rain is coming.

All but Sutil, Hulkenberg, Kobayashi and di Grassi are on track as Webber (hard) improves to fifth with a 34.680.

A 33.992 sees Schumacher (soft) go second, splitting the McLarens. Former teammate Massa improves to fifth with a 34.182.