Ahead of today's opening session the air temperature is 12.5 degrees C, while the track temperature is 15.4 degrees.

It is cold and wet following overnight - and early morning - rain, with a 90% chance of further downpours... welcome to Spa.

Due to the conditions, with drivers not wishing to take unnecessary risks, especially following the events at the start of the Hungarian Grand Prix, it is likely that we will see little running in the opening phase of the session.

The lights go green but there is understandably no rush to action.

However, as the sun attempts to break through the thick cloud covering the region there is the prospect of action to follow... eventually.

After a few minutes the Ferrari pair head out, followed by Schumacher.

Despite the conditions race control has not declared the session wet.

As more drivers head out, all on inters, Sainz reports that conditions are okay for slicks.

The Spaniard is subsequently told that there will be "no more rain" for the next half hour.

Eleven minutes in and as Hamilton heads out, Norris, Latifi, Verstappen and Russell remain the only no shows.

Norris subsequently heads out and posts the first time of the day (1:50.191). The McLaren driver is on mediums. "It's completely dry," he reports.

While most switch to slicks, Verstappen heads out on inters.

As Raikkonen spins at La Source, Vettel posts a 49.324.

The sun is shining.

A spin for Tsunoda at La Source, like Raikkonen he appears to be caught out by his cold tyres.

Gasly goes second (50.058), ahead of Norris, Alonso, Stroll, Ricciardo and Raikkonen.

A 49.060 sees Ricciardo go top, as Hamilton posts an exploratory 50.243.

As Verstappen pits, the other 19 drivers are on track, most are on hards though a couple are on mediums.

Amongst those on the yellow-banded rubber is Hungary winner Ocon, who posts a 48.087.

As Vettel goes second with a 48.119, Hamilton posts 48.224 to go fourth.

Stroll is warned by his team after he appears to impede Russell on the run up to Les Combes.

Ocon improves to 47.250.

Verstappen is back out, now on hards, and following a relatively slow out lap he begins his first flying lap of the day.

Quickest in the second sector, Verstappen crosses the line at 46.879 to go quickest by 0.340s. Ocon remains second, ahead of Gasly, Ricciardo, Perez, Sainz, Stroll, Vettel and Bottas.

Stroll, annoyed with traffic, lets loose a string of expletives.

"Feels massively slow on the straights," reports Hamilton.

As Perez goes second with a 47.167, Verstappen bangs in a 46.243, the Dutchman having slowed in the final sector due to waved double yellows in the pitlane.

Replay shows Raikkonen hitting the inside wall at the pitlane entrance, hence those waved double yellows.

As Latifi is the first driver to switch to softs, Leclerc complains of a "lot of understeer".

On those softs, Latifi improves to tenth with a 47.768. The Canadian subsequently splits the Red Bulls with a 47.101.

Verstappen consolidates his position with a 45.905, as Hamilton, still concerned about his pace, slips to 15th.

A 46.867 sees Stroll go second on the softs, only to be demoted when the similarly shod Ricciardo crosses the line at 46.683.

"We can still make a bigger step with the set-up," insists Russell as Vettel goes second with a 46.117.

As Sainz goes second (45.935), Hamilton and Bottas head out on softs.

Ocon is warned of light rain in ten minutes.

Quickest in the first and final sectors, Bottas goes quickest with a 45.199.

Having fitted a bigger rear wing, Hamilton goes quickest in S2, finally crossing the line at 48.224 following a poor final sector not helped by a misunderstanding with a slow Latifi on the racing line.

Quickest in S2, now on softs, Verstappen can only manage 45.496, which leaves him second.

A big moment for Leclerc as he runs wide and through the gravel trap at Turn 7.

"We have some drops at Turn 1 and also Turn 5," Sainz is warned.

Leclerc improves to fourth with a 45.818.

Another improvement from Verstappen (45.363), but he remains 0.164s off Bottas' pace. Hamilton pits having failed to improve.

The world champion heads out again but pits at the end of the lap, conditions appearing to have worsened as the rain begins to fall.

Mercedes issues are not helped when Bottas misses the pitlane entrance and has to complete another lap.

The session ends. Bottas is quickest, ahead of Verstappen, Gasly, Leclerc, Sainz, Perez, Vettel, Norris, Ocon and Alonso.

Stroll is eleventh, ahead of Ricciardo, Giovinazzi, Russell, Tsunoda, Latifi, Raikkonen, Hamilton, Mazepin and Schumacher.

While Mercedes, certainly as far as Bottas is concerned, appear to have the edge, Verstappen's pace on the hard tyre will not have gone unobserved by the German team.

Check out our Friday gallery from Spa, here.