Nico Rosberg continued his domination of the Red Bull Ring after banging in a supersoft tyre-shod lap of 1m 07.967s at the very beginning of the session, but as the track later dried Mercedes team mate Lewis Hamilton closed to within 0.019s.
The expected rain came in a veritable deluge after eight minutes, washing away plans to do single-lap speed runs, and then race-tyre runs.
As cars stopped running Daniel Ricciardo was third with a Red Bull supersoft run to 1m 08.649s, from supersoft Nico Hulkenberg on 1m 09.073s for Force India. Hamilton at that stage was only fifth with 1m 09.145s, but he had run only the soft tyres.
Kimi Raikkonen, meanwhile, had a big off at Turn 5 and though he negotiated his Ferrari out of the gravel, he never bettered 1m 17.809s as a result. Max Verstappen’s Red Bull stayed in the garage, still being repaired following his morning off, so he never got a dry lap.
It was 37 minutes before anyone ventured out again, as the track was drying at Turn 2 and beyond, but still slippery at Turn 1 and very wet at Turn 9. Perhaps suitably, it was the Red Bulls that led the return to action, Ricciardo enthusiastically opposite-locking his way out of the garage on intermediate tyres as the sky brightened, and Verstappen followed him.
For a long time conditions were at least 10s off the previous times, as Rosberg, Toro Rosso’s Daniil Kvyat, Verstappen, Ricciardo and Haas’s Romain Grosjean all slid wide at Turn 1, Hulkenberg, Manor’s Pascal Wehrlein and Force India’s Sergio Perez went off at Turn 8, and Verstappen spun at Turn 9.
With 25 minutes left, however, things began to improve as the high humidity helped the track to dry. Perez lapped in 1m 15.9s but it was Raikkonen who was the first to improve, jumping from 17th to eighth with 1m 09.991s.
Hamilton then had a good lap going until he came upon Esteban Gutierrez’s slower Haas and had to brake hard in the second sector; next time around the world champion improved to 1m 07.986s to go second. He had a faster still lap going until deciding to abort and swing alongside the pit wall before getting back up to speed, and Rosberg likewise cut short a better lap after setting the best first and second sector times.
Hulkenberg also went quicker, taking third with 1m 08.580s to beat Vettel by nine-thousandths. The Ferrari driver’s attempt to improve ended when the SF16-H snapped sideways on him braking for Turn 2 and he was lucky to stop before his spinning machine touched the tyre wall. “I don’t know what happened there,” he told his crew over the radio. “I just lost the car completely.”
Ricciardo ended up fifth on 1m 08.649s and Toro Rosso’s Carlos Sainz headed Verstappen with 1m 08.713s to 1m 08.761s. Raikkonen, Williams’ Valtteri Bottas and McLaren’s Jenson Button completed the top 10, all within half a second of Hulkenberg.