Felipe Massa led a Williams 1-2 during a truncated, rain-affected final practice session for the Italian Grand Prix.
Heavy rain and thunderstorms struck the circuit during Friday evening and persistent wet weather greeted the paddock upon arrival on Saturday morning.
The preceding GP3 qualifying session was cancelled due to the track conditions, with standing water accentuated by the continued heavy rainfall.
With five minutes to go before the schedule start, Race Control informed that the session had been ‘delayed indefinitely’ due to the conditions.
Safety Car driver Bernd Maylander completed a couple of laps at occasional intervals in order to assess the situation.
Eventually, the signal was given that the session would begin at 11:44 as the rain eased slightly, enabling 16 minutes of running to take place.
All 20 drivers took to the circuit on Pirelli's Full Wet tyres, but only seven opted to set a timed lap, with Massa clocking a 1:40.660 to finish 0.228s clear of team-mate Lance Stroll.
Renault’s Nico Hülkenberg and Jolyon Palmer took third and fifth, sandwiching Toro Rosso’s Carlos Sainz Jr., who was the busiest driver, albeit completing five laps.
Marcus Ericsson and Daniil Kvyat were the only other drivers to record a timed lap.
With air temperature at only 13°c, and with little wind, conditions are unlikely to significantly improve prior to qualifying.