Ahead of today's second session the air temperature is 31.1 degrees C, while the track temperature is 45.2 degrees.
With their various updates having been given their first try, over the next hour we should witness the teams continue to acquire that all-important data.
As a reminder, the updates are as follows: Mercedes has a new front wing endplate, floor and rear brake winglets, whilst Red Bull has new front wing flaps and a new floor.
For Ferrari it's a new floor, rear brake winglets and rear wing, while McLaren brings new front wing flaps, front suspension, brake ducts, floor, diffusor, engine cover, cooling louvres, rear wing and rear brake winglets.
Alpine has a new rear wing, front wing endplate and rear brake winglets, whilst Alpha Tauri merely has a new rear wing.
Aston Martin has a new floor, sidepod, bodywork, cooling louvres, rear wing and Halo, while Williams brings new front wing flaps, rear wing and rear brake winglets.
Alfa Romeo is another team with an impressive array of updates, the Hinwil-based outfit having brought a new front wing endplate and flaps, front suspension, engine cover, floor, cooling louvres, rear suspension and rear wing.
Though it is far too early to be making assumptions, it did appear that Mercedes seems to have brought the porpoising under control.
Having handed over their cars for the opening session, this afternoon Sergio Perez, Alex Albon and Sergio Perez get their first taste of Barcelona since pre-season testing.
The lights go green and Albon is first out of the box, followed by Vettel, Ocon, Stroll and Perez. Sainz is another early bird as the mediums appear to be the order of the day, though a few drivers are on hards.
In no time at all there are 17 drivers on track, Ricciardo, Alonso and Bottas the 'no shows'.
Of the first wave, Verstappen goes quickest (20.932), ahead of Sainz, Russell, Perez and Schumacher.
Hamilton goes third with a 21.894, edging out his Mercedes teammate.
The leading seven times are set with the medium, while Magnussen is the leading hard runner in eighth.
Leclerc's first flying lap sees the Monegasque go third with a 20.995.
A mistake sees Norris go off and through the gravel at Turn 7.
"Something's broke," reports Bottas as he pulls off track at the end of the main straight, thereby bringing out the yellow flags. The Finn had previously posted a 21.828 to go sixth.
The VSC is deployed.
"So dangerous this guy," says Sainz of no one in particular as the stewards have noted a Turn 4 incident involving Norris and Schumacher.
"I want to avoid this bouncing through Turns 3 and 9," reports Russell. "Bottoming is on the limit but it is manageable," he adds. The Briton is currently 5th.
"A little bit, yeah," replies Ricciardo when asked if the high-speed ride costing performance.
Switching to the softs, the qualifying sims get underway, and Vettel goes quickest with a 2.703, as Perez goes second (20.792), the Mexican also on the softs.
On the red-banded rubber, Verstappen stops the clock at 20.006.
As Sainz begins his qualifying sim, Stroll goes sixth with a 21.249. Sainz crosses the line at 19.990.
As Leclerc winds up ahead of his first flying lap, the Ferrari driver encounters a lot of traffic in the final sector. With the wind picking up he is also set to encounter a strong head wind in Turn 1.
Quickest in the second sector, the world championship leader crosses the line at 19.670 to go quickest by 0.320.
Moments before Leclerc went quickest, Alonso had posted a 20.203 to go third, the Spaniard now demoted to fourth.
Russell splits the Ferrari pair with a 19.787 as Hamilton heads out on a fresh set of softs.
PBs in all three sectors sees the seven-time world champion go third with a 19.874.
"Every time we touch the throttle we are sideways," reports Gasly.
The qualifying sims out of the way, attention now switches to Sunday afternoon and high-fuel long runs.
It appears that Norris' session is over after one too many close encounters with the kerbs.
While Verstappen remains on the mediums, Perez switches to the softs. Similarly, Ferrari has its drivers on a spit strategy.
After 17 laps, it is understandable that Leclerc is concerned at the wear to his mediums. "They're going into pieces," he warns.
Stroll has completed the most lap (26), ahead of Vettel, Albon and Sainz, who have all completed 25.
Despite being the only team not to have any upgrades here, Haas will surely be chuffed to have its drivers 10th (Schumacher) and 12th (Magnussen).
"I went off into the gravel," confirms Perez following a trip through the kitty litter at Turn 8.
The session ends. Leclerc is quickest, ahead of Russell, Hamilton, Sainz, Verstappen, Alonso, Perez, Vettel, Ocon and Schumacher.
Gasly is eleventh, ahead of Magnussen, Stroll, Tsunoda, Ricciardo, Bottas, Zhou, Albon, Latifi and Norris.
So, Ferrari continues to set the pace, while, certainly from Russell's point of view, Mercedes porpoising issue isn't entirely resolved.
While Red Bull has yet to show its hand, Alpine appears to be best of the rest, while Haas is also looking surprisingly good for a team with no updates.