Heavy rain in the 30 minutes leading up to the hour-long session in Suzuka meant no cars went out when the pit lane opened, even though there was no more precipitation when the green exit light came on.
Kevin Magnussen became the first driver to leave after five minutes and he was thus joined by home hero Yuki Tsunoda – although neither driver completed a timed lap, with Tsunoda reporting “a few rivers” on the track at the end of the first sector.
Nicholas Latifi, Mick Schumacher and Lance Stroll also ventured out towards the end of the first 15 minutes, but it was only the Haas driver who stayed out to set a time. Schumacher’s 1m52.237s therefore set the benchmark at 1m52.37s, set with fully wet tires.
They were soon joined by more cars, with Leclerc saying he thought conditions would soon be suitable for intermediates.
His teammate Carlos Sainz beat Schumacher’s time with his first racer on a 1m49.952s, before Leclerc, after a few seconds behind the road, took first place with a 1m49.103s.
The Ferraris continued to circulate, posting faster times on the full wet track – first with Leclerc’s 1m38.104s and Sainz, who had complained of hearing a strange noise from his engine, which he thought was the turbo, crept ahead of a 1m47 .758s.
Max Verstappen, Esteban Ocon and Valtteri Bottas were the first drivers to start on intermediates just after halfway through, the first two before their first laps in FP1.
As this has almost become a trademark of Verstappen in FP1s this year, he went straight to the top of the time with his first racer, a 1m44.059s.
Bottas and Ocon then also went in for the Ferrari drivers using the green-walled rubber, as did Singapore winner Perez – albeit 2.886 seconds behind his teammate, who by then had completed a second flyer to set the best time. improve to a 1m43. 362s.
Ocon’s second flying lap then put him ahead of 1m43,022s, before the rain returned and spray increased around the 3.6 mile lap.
But that didn’t stop the times from improving, with the Ferrari drivers now on the inters and flying as the final 20 minutes approached. Leclerc came back into the lead on a 1m42.634s which showed a huge slide that almost came off the kerbs coming out of the second Degner turn, before Sainz beat it with a 1m42.563s.
Then came Alonso, who made his way to the fastest times in the first two sectors (Sainz retained the fastest last sector) and first place on a 1m42.248s.
Deteriorating conditions in the final 15 minutes caused several drivers to have moments off-track, including the Ferraris. Sainz raced through to the drain at the Spoon corner, while Leclerc slid across the curbs between the Degners in one lap before completely skating into the gravel at that point on his next tour.
Leclerc returned to full wet tires for a final lap, but soon joined the rest of his colleagues in the pits.
Alfa Romeo pair Zhou Guanyu and Bottas led a massive final reconnaissance in the final few minutes, but no driver improved their times in full rain, with Bottas sliding into lap two with 130R.
The 10 drivers who did get out – including the Ferrari pair – were instead sent out to wet the practice sessions on the straight, as is typical of any practice session.
That left the final order in the top three as Ocon, Magnussen, Verstappen, Schumacher and Lando Norris, the McLaren driver had to pit after receiving an engine warning during the early laps.
Bottas and Perez completed the top 10, closing the gap to the top spot by almost two seconds.
Lewis Hamilton was 13th behind Daniel Ricciardo, who had to run over the chicane just as the rain started pouring heavily again in the closing stages.
The other driver taking a ride in the gravel was Latifi, the Williams driver stalled and slipped at low speed at the hairpin just after 30 minutes had finished.
Wet weather is expected to persist into the first day of F1 action at Suzuka since 2019.