Max Verstappen topped final Formula 1 practice for the Spanish Grand Prix heavily influenced by confusion over weather conditions.
The Dutchman set a benchmark of 1:13.664 to finish 0.250s faster than Red Bull teammate Sergio Perez, with Mercedes' Lewis Hamilton third.
All representative lap times were set in the opening 10 minutes of the session, played to a backdrop of angry black clouds and lightning.
Whilst rain fell mid-session, conditions never worsened enough for Intermediate running but the track dampened enough to create struggles on the Softs.
Result Free practice 3 - Spanish
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Drivers explore conditions
Drivers rushed to the circuit as the green light illuminated at the end of the pit lane, with all drivers but the Alpine duo on Soft tyres.
But dry weather running ended with Logan Sargeant's crash with 50 minutes left on the clock - the Williams driver becoming the first victim of the updated final sector layout when clipping the kerb at the last corner to unsettle his car and slide into the barriers.
Rain began falling lightly during the subsequent red flag period and though the precipitation wasn't heavy enough initially, teams were hesitant to take to retake to the track.
Lando Norris finally broke the silence to test the conditions on the Intermediate tyres with 28 minutes to go, though the McLaren driver returned to the pits after his out-lap. Ferrari followed at the start of the final third for an exploration of grip. This triggered a flurry of activity in the closing stages with valuable information gathered for what could be a tricky qualifying session.
Hamilton was one of a minority of drivers that didn't return to the track, with teammate George Russell was confused by the conditions, telling Mercedes: "It's definitely raining, just the track doesn't seem that wet."
The lack of moisture on the track surface prompted an experiment on slick tyres for Norris whilst Lance Stroll slid wide at Turn 5 for Aston Martin and Pierre Gasly suffered a similar fate at Turn 7.
Norris delivered a lap six seconds faster than his Intermediate time on a set of Softs, although this was eight seconds slower than his best effort in the opening stages.
Ferrari again reacted to McLaren's pioneering efforts, with both drivers testing out the Softs, with everyone else following. Verstappen, however, conceded he was 'not comfortable pushing' in the conditions.
Carlos Sainz was the lead Ferrari in fourth ahead of compatriot Fernando Alonso, who had put his Aston Martin second to Verstappen at the end of Friday's running.
Russell finished sixth with Charles Leclerc seventh and Alfa Romeo's Valtteri Bottas again showing performance in eighth.
AlphaTauri driver Yuki Tsunoda and Norris rounded out the top 10, though with only one flying lap completed by the field, the pecking order is likely to change by the end of qualifying.