Pierre Gasly topped final practice for the Turkish Grand Prix in difficult conditions after morning rain at Istanbul Park.
Frenchman Gasly posted a time of a one minute 30.447secs on intermediate tyres to lead Max Verstappen as the track dried rapidly throughout the session.
Sergio Perez finished third in a Honda-powered one-two-three as Mercedes opted not to run as the conditions improved.
George Russell failed to set a lap time after triggering the first red flag period of the weekend, spinning into the gravel after switching from full wet tyres to intermediates.
AlphaTauri driver Gasly was the first to venture out of the pits after 10 minutes of no track running and after a switch to intermediate tyres some eight minutes later became the first to spin in tricky conditions.
The AlphaTauri aquaplaned through the fast turn 11, a move followed shortly by Nikita Mazepin.
George Russell's session was cut short with 37 minutes remaining as the Williams rotated itself into the gravel on the outside of turn two. Russell was left stranded and red flags were thrown.
After a five minute delay, there was a flurry of track action although Friday's fastest man Hamilton lost grip at turn nine, allowing Verstappen to set what was then the fastest time by over a second.
The Dutchman suffered a spin of his own on the very next lap at the same turn, although Verstappen seemed pleased with his efforts, boasting "nice 360" over team radio.
Hamilton and Mercedes called time early in the session, not running in the final 20 minutes as track conditions improved and times tumbled.
The Honda teams looked strong in the changing conditions though with Gasly finding pace to leap ahead of Verstappen and Perez.
Carlos Sainz, who will start at the back of the grid after changing his PU, completed the third-most laps of anybody and finished fourth, with team-mate Charles Leclerc fifth.
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