Ahead of today's second free practice session the air temperature is 17 degrees while the track temperature is 16 degrees.

It is raining. However, unlike this morning's intermittent light rain, this appears far more settled… and heavier.

Jenson Button topped the timesheets earlier however, the McLaren driver posted his time at the very start of the session before the weather began changing. Nonetheless, McLaren, following disappointing outings at Valencia and Silverstone, will be buoyed to have Lewis Hamilton finish second, the Woking outfit having introduced a raft of updates here.

Fernando Alonso was third quickest as Ferrari continues to improve, ahead of Schumacher, Perez and Hulkenberg.

Main focus of attention this morning, other than the weather, was the Lotus of Kimi Raikkonen, the Finn running an aero update about which the Enstone outfit is saying very little and working abnormally hard to shield from prying eyes.

"An aerodynamic prototype was tested on Kimi's car," Lotus press officer Andy Stobart told Mat Coch. "It's a proof of concept only and unlikely to be raced." The consensus in the paddock is that it's a double DRS device based on the concept of that used by Mercedes.

The Williams crew has been kept busy during the break, having to replace pretty much everything at the rear of the car following Bottas' off this morning.

The lights go green but nobody is moving, Race Control that conditions will remain like this for "one hour at least".

Six minutes into the session, Senna comes out for an installation lap. The rooster tail and his tippy-toe approach confirming the treacherousness of the conditions.

Although there's no sign of the rain abating, seventeen minutes into the session, Vergne, Pic and Rosberg head down the pitlane to dip a tow in the water… literally. Rosberg is warned that there are several places, particularly Turns 8 and 10, where there are small rivers running across the track.

Despite a little moment, Vergne posts a 43.330, the first time of the afternoon. Moments later, Rosberg posts 43.222.

There are cheers and waves of appreciation when Vettel heads out of the Red Bull garage, Michael Schumacher the only home driver not currently on track.

The rain ease off slightly, and as Webber, Kobayashi and Schumacher get to work, Race Control reveals that another heavy shower is expected in twenty minutes.

Rosberg improves with a 39.021 as Webber goes third (39.721) ahead of Vettel, Schumacher and Ricciardo. Vergne makes full use of the run-off at Turn 1.

As Rosberg heads back to the pits, with 1:01.12 on the clock, all but the McLarens, Ferrari and de la Rosa have been out.

As di Resta runs wide in the final corner, Schumacher goes quickest in S1. The old 'rain master' maintains a strong pace in the second sector crossing the line at 38.194 to displace Vettel who had just posted 38.243.

The McLaren duo finally leave the pits, however, no sign of de la Rosa or the Ferraris.

As Perez has a big wobble and runs wide, Kobayashi goes quickest in S2 but remains ninth overall.

Button's first flying lap sees the Englishman go sixteenth (40.896) as Vergne posts 38.051 to take the top spot.

Rosberg is the first driver to make the switch to inters, the German currently seventh (39.021). Elsewhere, Hamilton posts 41.841 to go twentieth.

On his first flying lap Alonso, on inters, goes quickest, the Spaniard throwing down the gauntlet with a 37.395. Hamilton improves to thirteenth (39.350).

As Rosberg goes quickest (37.285) his rivals realise that now might be the time to follow his example and switch from full wets to inters.

Webber switches to inters also as Hamilton (wets) goes quickest in S2, ultimately crossing the line at 37.646 to go fourth.