Ahead of today's opening session, the air temperature is 18 degrees C, while the track temperature is 19 degrees. It is raining, and it has been raining for much of the morning thus far

"It is expected to dry out this afternoon but then be wet again tomorrow morning and then dry thereafter," texts Bob Constanduros fifteen minutes before the session is due to begin, ominously adding; "today reminds me of the day that Didier Pironi had his accident."

Of course, the less than favourable conditions are going to hamper those teams hoping to run new components today, with particular reference to McLaren which intended running its blown diffuser again.

Sakon Yamamoto is replacing Karun Chandhok this weekend while Fairuz Fauzy is in Heikki Kovalainen's Lotus for this session.

Tyre options are hard and super-soft but it is unlikely that we'll be seeing much of these this morning.

When the lights go green Jarno Trulli leads the way, followed by Yamamoto, Fauzy, Liuzzi, Alguersuari and Buemi.

Five minutes into the session, Nico Hulkenberg, having completed his installation lap, stays out, giving the rain-drenched fans something to actually look at. However, at the end of the second lap he is thankful to dive back into the pits. It's nasty out there.

Rosberg and Vettel also stay out for second laps, the Mercedes getting well out of shape in the hairpin. All but the McLaren duo have been out.

The Saubers are sporting special logos to mark the fact that the team is celebrating 40 years in motorsport this weekend. Sadly, it is one of the few logos on the Swiss car.

Alguersuari is the first driver to go out for a second run, the Toro Rosso driver immediately going wide at the hairpin. The Spaniard subsequently posts the first time of the day, crossing the line at 1:41.068. Next time around, Jaime raises the benchmark with a 36.605 as Vettel goes second with a 36.905. Only these two are on track.

As Webber, Buemi and Kobayashi head down the pitlane, Vettel improves with a 34.796.

More and more drivers take to the track as Alguersuari goes quickest (33.402), ahead of Vettel, Webber, Massa, Hulkenberg, Kobayashi and Buemi.

Massa goes quickest with a 31.981 but this is soon beaten by Webber with a 31.019. Elsewhere, Petrov runs wide and Fauzy goes cross-country.

A 30.864 sees Rosberg go quickest, as the rain continues to stop-start-stop-start and stop again.

Forty minutes into the session - with Rosberg still quickest, ahead of Hulkenberg, Massa and Sutil - Alguersuari is the first driver to switch to intermediates. Elsewhere, Kubica and Massa have excursions into the German countryside and Hulkenberg has a big spin, the German - like Alguersuari - having switched to inters.

Even the rain-master, Michael Schumacher, is not immune, the German running wide, while Button complains of poor visibility and lots of understeer.

Alonso goes quickest with a 30.229, as Vettel goes second and Barrichello third. All but Fauzy, Trulli, Glock, di Grassi and Hamilton have posted times.

Rosberg (inters) goes quickest in the first two sectors, finally crossing the line at 29.419, the first driver to break the 1:29s barrier. Norbert Haug watches his monitor impassively.

With the rain now having ceased for quite a few minutes the inters appear to be the tyre to be on, a number of drivers break the 1:29s barrier with Webber going quickest of all with a 29.048.

Shortly after Vettel breaks the 1:28s barrier, Sutil goes quickest of all with a 28.411, the German revelling in the conditions.

Massa gets it all wrong at Mobil, the corner where the track enters the 'stadium'. Despite a long trek through the gravel he is able to continue. Elsewhere, Sutil posts 27.846.

Hamilton's session is over almost before it's begun, the McLaren driver losing the back of the car as he exits Turn 4 and clouting barriers. The back of the MP4-25 is quite badly damaged which is going to severely compromise the team's plans for the weekend, certainly in terms of the blown diffuser. "I hit the wall, car's damaged," he tells his crew, the tone of his voice saying it all.