Ahead of today's free practice session, the air temperature is 22 degrees C, while the track temperature is 30 degrees. Behind the heavy cloud the sun is doing its very best to break through. However, there was rain overnight and further rain is expected later in the day.

Yesterday, Red Bull set the pace in both sessions, with Ferrari giving the Austrian team a run for its money, both teams seemingly benefiting from the legally flexing front wings.

While both McLaren and Mercedes struggled, Renault was on the pace with Vitaly Petrov finishing ahead of his Polish teammate.

The tyre choice this weekend is between medium (prime) and super-soft (option).

When the lights go green, Kovalainen leads the way followed by Yamamoto, Sutil, Alguersuari, Liuzzi and Vettel.

With oil having been dropped on the track by one of the Formula BMW runners, there is white cement dust from Turn 2 almost all the way to Turn 4.

Five minutes into the session all but Hamilton have been out for an installation lap, yesterday's rubber having been washed away by the overnight rain.

Vettel says there is very little grip and suggests that in the first half of the session it will be pretty much pointless expecting any serious data.

Hamilton completes his installation lap but nobody appears eager to go out for a second run.

As Martin Whitmarsh and Stefano Domenicali appear to share a joke in the pitlane, Kovalainen, Yamamoto and di Grassi return to the track.

Of the three Kovalainen posts the fastest lap, the Finn crossing the line at 27.671. Moments later, teammate Jarno Trulli posts 27.649.

Webber is the first of the big guns to come out for a second run, while di Grassi does a good job of cleaning up the cement dust.

Alguersuari posts 25.343 but Hulkenberg is on a hot lap finally crossing the line at 24.664. Elsewhere, Liuzzi runs wide at Turn 13.

Webber's first flying lap sees the Australian - not unsurprisingly - go quickest with a 23.149. Elsewhere, Vettel, Hamilton and Schumacher head down the pitlane.

Hulkenberg raises the benchmark with a 22.686, the German likes this track having won here in GP2.

On his first flying lap Vettel goes quickest with a 21.594 but he is almost instantly leapfrogged by his teammate with a 21.634.

De la Rosa goes fourth, ahead of Schumacher, Kubica and Barrichello. Petrov, Massa, Alonso and Hamilton are the only drivers yet to post a time.

A 21.087 sees Webber consolidate his top spot as Hamilton posts 22.277 to go third. While Alonso and Button are on track, Massa is still in his garage.

Petrov locks-up at the entry to Turn 1 and consequently runs wide. Elsewhere, Vettel goes quickest in S1 and S2 ultimately crossing the line at 20.966.

Alonso goes third with a 22.209, albeit 1.243s off Vettel's pace. Moments later, Rosberg goes third with a 22.149 as Vettel improves again, crossing the line at 20.261.

Petrov goes quickest in the first sector, however he makes a complete cock-up of Turn 12 and runs wide.

Button goes fifth with a 21.922 slotting in behind his teammate and ahead of Massa. Elsewhere, Senna is another driver to get it wrong at Turn 13.

On board footage from Button's car shows the McLaren losing a second in S2. In the McLaren garage there is a look of resignation on the faces of the crewmembers. Next time around, the 2009 champion leapfrogs his teammate with a 21.781.

A driveshaft problem appears to have sidelined Liuzzi, the Italian not likely to play any further part in this session.

With eighteen minutes remaining, it won't be long before we see drivers start focussing on qualifying, switching to the option tyres and low fuel.