Ahead of today's opening session, the air temperature is 22 degrees C, while the track temperature is 24 degrees. It is somewhat overcast, with a 60% chance of rain. Indeed we are expecting rain today and tomorrow but sunshine on Sunday.

As was the case in Belgium last week, a number of drivers are running the Halo device in this session, not least Alonso and Sainz. Also, as in Belgium, there are no reserve drivers on duty.

Antonio Giovinazzi was due to drive Magnussen's car, but with this possibly being the only dry practice session the team opted to leave the Dane in the car.

Monza being Monza, the teams are running a variety of aero packages, some of them, Renault for example, bringing as many as three different front wings.

As for rear wings, as ever they will be as flat as possible, hence the practice of referring to them as 'dinner trays' - though hopefully, unlike the Pitpass version - they do not have pictures of cats on them.

With an eye on those clouds, there is a queue at the end of the pitlane, headed by Ricciardo.

As the drivers head out, work continues on Verstappen's car, Red Bull having discovered an issue with his floor earlier this morning.

Only Bottas, Ericsson, Massa, Stroll and Palmer stay out for a second lap.

The Brazilian, a favourite with the Tifosi following his time with Ferrari, posts 27.666, with his teammate posting 27.877 moments later. Both are on the supersofts. All the other running thus far - for what it's worth - has been on the mediums.

Stroll improves to 26.554 as Wehrlein heads out again. Indeed, the German gets an early blue flag as he gets in the way of a frustrated Massa. By the end of Sunday afternoon, the Sauber driver will be sick to death of the colour blue.

Nine minutes into the session, Verstappen heads out.

AS Massa improves to 25.553, Hamilton is on a hot lap, the Briton going quickest in the first two sectors before crossing the line at 23.964. The Briton is on the softs.

Perez goes second with a 24.814 as work resumes on Verstappen's car.

A 24.340 from Bottas makes it a Mercedes 1-2, both drivers on the yellow-banded rubber, the Mercedes no fan of the supersoft.

An early excursion for Stroll who misses the first chicane. "I've got a big flat spot now," he wails.

Raikkonen is told that the wind is "picking up", which could signal the arrival of the rain.

As the Ferraris head out, both on the supers, Hamilton improves to 22.861.

Raikkonen's first lap is a conservative 24.974, as Hamilton misses the first chicane.

Magnussen gets a cheeky tow from Vettel and then gets it completely wrong at the first chicane, thereby allowing German to re-pass him.

Bottas takes the top spot with a 22.523 as Vettel goes fourth with a 24.396.

As misses the first chicane again, after 22 minutes, all but Palmer and Verstappen have posted times.

Grosjean runs wide in T8, the Frenchman claiming yesterday that he is not always complaining about his brakes and that the media is stirring things up.

Ricciardo goes fifth with a 23.934, while moments later teammate Verstappen posts a 24.710 to go tenth.

As Vettel improves to third (23.654), Grosjean gets the second chicane.

Vettel reports light rain at Turns 8, 9 and 10, as Hamilton misses the second chicane.

PBs in the final two sectors sees Raikkonen improve to fifth with a 23.682.

Perez remains fourth (23.485), while his bestest buddy is currently seventh on 23.879.

Vettel misses the first chicane as Verstappen reports that he needs to go forward with his brake balance.

After thirty minutes, Palmer is finally on track.

Verstappen improves to fifth with a 23.566 as Palmer posts 26.342. The Briton reports a lot of understeer at lower speeds... subsequently proving it by going off at the first chicane.

As we reach the stage where drivers hand back their extra set of tyres, it's: Bottas, Hamilton, Vettel, Perez, Verstappen, Raikkonen, Ricciardo, Ocon, Sainz and Kvyat.

Check out our Friday gallery from Monza, here.