While Mercedes came out of yesterday looking as strong as ever, albeit with Williams heading the pack behind as opposed to Red Bull, all that could be about to go out of the window.

Not for the first time the weather gods - or whatever they call them in this neck of the woods - look likely to have a say.

There was rain following yesterday's final session, rain overnight, and more this morning, and the official meteorologists predict that this will continue for the rest of the weekend.

Such conditions are called "changeable", and as we all know there are certain drivers who thrive in such weather.

Rain, and especially intermittent rain, is the great leveller, in terms of drivers and their cars.

Ironically, the timesheet following FP2 had the look of Noah's Ark about it, the teams pretty much lining up two-by-two.

Ahead of the start of the session, which has been declared wet, the air temperature is 19 degrees C, while the tack temperature is 23 degrees.

Fact is, though the session is officially "wet", it is no longer raining, merely damp. Indeed, much of the track is dry, but by the look of the skies that will soon change.

Indeed it does, just moments before the green light the heavens open and a strong wind ensures that everyone gets nice and wet.

Raikkonen gets things underway, the Finn on full wets. He is followed by Vettel, Massa and Wehrlein. The latter on Inters.

"It's not really wet, no standing water, just damp," reports Vettel.

One man not going anywhere anytime soon is Alonso who is in the McLaren hospitality unit watching proceedings on TV. He isn't even wearing his overalls.

"It's very dry out here," says Hamilton, "we should be on slicks." He is told to pit. Meanwhile, teammate Rosberg heads out on full wets.

Ten minutes in and Hamilton is the first driver to make the switch to slicks, the Briton bolting on a set of softs. As he heads out he is told to "exercise caution".

The world champion has the track to himself as rivals monitor his progress. Running wide in T4 he finally crosses the line at 1:20.910, the first time of the day. Next time around he improves to 16.980 having once again gone wide in T4.

Wehrlein, Bottas and Massa all head out on the yellow-banded tyres.

Work continues on Alonso's car in the McLaren garage. Initial fears that a gearbox change might be needed, with grid penalty, there are hopes that the issue may not be as serious.

Yellow flags are waved as an umbrella is blown on to the track.

Bottas posts 15.048 to go quickest, while Massa can only manage 24.466, the Brazilian having slowed for that umbrella.

Massa improves to 13.848 subsequently reporting "a little bit more rain".

"Let me know on the radio if there is any rain or something like that," drawls Raikkonen. Something like rain?

Verstappen goes third (14.702) but is demoted when Raikkonen goes quickest with a 12.860.

"Small drizzle on the main straight," Sainz is warned.

Nonetheless, more and more drivers are switching to slicks.

As Ricciardo goes second (13.762), Raikkonen goes quickest in S1. He maintains the pace in S2, finally crossing the line at 12.530 having lost time in the final sector.

A 13.198 sees Vettel go second, demoting Hulkenberg who had posted 13.615, no doubt Maurizio Arrivabene hoping that these conditions continue.

Of the 16 drivers who have posted times, Rosberg and Hamilton are 14th and 15th, the Mercedes duo focussing on longer runs already.

A lock-up for Vettel who closes to within 0.131s of his teammate.

Unseen, Alonso has posted 14.209 to take 12th, so that gearbox change was a false alarm.

"Long runs underway for our boys on this run," confirms Mercedes, "both through the 10 lap barrier overall, 5/7 apiece in the stint so far..."

Check out our Saturday gallery from Interlagos, here.