Lewis Hamilton emerged from the garage to set one lap time and top FP2 for the United States Grand Prix by a second in another wet practice session in Austin.
There was no running at all in the first half of the session due to heavy rain which left plenty of standing water on track, and early laps from Brendon Hartley, Stoffel Vandoorne and Kimi Raikkonen all took place on the full wet tire.
Hartley was by far the most productive driver after sitting out FP1 in place of Sean Gelael, with the New Zealander completing 19 laps, but also running off track at the Turn 11 hairpin late on.
Conditions improved to allow intermediate running toward the end of the session, and in the final ten minutes the majority of drivers tested conditions, with Hamilton hitting the track to do one timed lap and set the pace again with a 1m48.716s.
Pierre Gasly was second fastest as he also managed ten laps, ending up slightly over a second slower than Hamilton despite setting the fastest middle sector overall on his final timed effort. Gasly edged out his future Red Bull teammate Max Verstappen, who was 0.07s adrift in third place.
The two Toro Rossos were so productive because they were the only drivers to use a new set of intermediate tires in FP2. The rest of the field opted to save tires for qualifying — which is also forecast to be wet — but both Toro Rossos will start from the back of the grid as a result of Honda power unit changes.
Behind Verstappen, Fernando Alonso was three seconds off the pace in fourth place, ahead of Nico Hulkenberg, Hartley, Marcus Ericsson and Vandoorne. Having spent this week testing in Valencia ahead of his Formula E debut, Vandoorne only arrived in Austin on Thursday evening and sat out FP1 as Lando Norris drove, so his ten laps were also his first of the weekend.
The two Ferraris of Raikkonen and Sebastian Vettel rounded out the top ten, while only Lance Stroll in 12th set his best time on full wet tires. It was learned after the session that Vettel was given a three-place grid penalty at for failing to slow sufficiently under red flags during the opening practice session.
The conditions were so bad that four drivers — Valtteri Bottas, Daniel Ricciardo, Kevin Magnussen and Romain Grosjean — all sat out the full session, while Carlos Sainz only completed two laps and didn’t set a time.