Ahead of today's free practice session, the air temperature is 15 degrees C, while the track temperature is 16 degrees. It is overcast and there is a serious threat of rain, not only during this session but later this afternoon during qualifying.

Indeed, at this very moment, with the session about to begin, the rain begins to fall.

The lights go green and first out on track is Yuji Ide, who is followed by Massa, Liuzzi, Monteiro and Albers.

Michael Schumacher, Button, Barrichello and Trulli are the other 'early risers'.

Ide is the first driver to post a time, however it is Jarno Trulli who is first to post a sensible time, crossing the line at 1:50.442.

In the minutes that follow, more and more drivers go out, and consequently the times begin to tumble. Montoya and Fisichella both spin, but both are able to continue.

For a few moments it stops raining, allowing Fisichella and Villeneuve to post sub 1:40s times, but pretty soon it is raining again.

The weather is pretty bad, one might almost describe it as stormy, consequently most of the drivers opt to wait in the pits, except for Alonso and Rosberg.

Alonso goes third, going quickest of all in the second sector, however he loses time in the first and final sectors, which is where the track is most wet. Rosberg returns to the WilliamsF1 garage, leaving the Spaniard to have a splash about in the park on his own.

Alonso goes quickest with a 1:39.654, having posted the best time in two of the sectors, surely a sign that conditions are improving.

The rain has stopped, but it is still very damp. Consequently, both Massa and Ide have spins. Button also has a moment.

At half-time, only 16 drivers have posted times, with Alonso quickest, ahead of Fisichella, Button, Barrichello and Villeneuve.

Conditions are clearly improving however, as Button goes quickest (39.00), and Liuzzi goes third (39.799).

As Klien spins, Fisichella raises the benchmark with a 1:36.419, while Heidfeld and Villeneuve go second and third for BMW.

Fisichella shave another five-thousandths of a second off his time, as Villeneuve takes second. The Canadian will forfeit ten grid spots following an engine change on Friday.

The session is over for Albers who spins off for the second time this weekend. The yellow flags are brought out as he climbs from the car. Elsewhere, Michael Schumacher has gone fourth with a 1:38.405.

Next time around the German improves to third with a 1:37.805, only Fisichella and Villeneuve have gone quicker.

With eighteen minutes remaining, Massa goes quickest in the first sector, 0.4s faster than the previous best. The Brazilian crosses the line at 1:36.506 to go second.

The track is clearly drying, as Barrichello now goes quickest in the first sector. The Honda driver goes third (37.481), as Webber goes seventh, behind his former Jaguar teammate, Christian Klien. Meanwhile, Liuzzi has another spin.

A 1:36.281 sees Villeneuve go quickest, with ten minutes remaining. However, the Canadian is the only driver on track.

As the driver prepare for one final attempt, the rain begins falling again. It's only a light shower, but it's enough. Only Speed, Liuzzi, Ralf, Trulli and Ide are on track.

As Speed goes quickest in the first sector, he is eclipsed by Trulli, who goes almost a full second quicker than anyone else in that particular sector. He loses a little ground in the second sector, but completes the lap in 1:37.492, which is good enough for fifth.

Moments later however, he's demoted by his teammate, who goes third with a 1:36.445. Meanwhile, Liuzzi goes second - yes second - with a 1:36.373, in the Toro Rosso.

Sato finally posts a time, his 1:41.448, is good enough for nineteenth, which puts him ahead of the two McLarens.

Heidfeld reclaims the top spot with a 1:35.335, which gives BMW a perfect 1-2.

As the session comes to a close, Michael improves to seventh, but there are no other improvements.

The session ends with Heidfeld quickest, ahead of Villeneuve, Liuzzi, Fisichella, Ralf, Massa, Michael, Barrichello, Trulli and Speed.

Qualifying kicks off in two hours, and according to the weather forecasters we can expect much of the same, intermittent rain showers.

It should be interesting…