Williams drivers Felipe Massa and Lance Stroll set the pace as heavy rain rendered the final Italian Grand Prix practice virtually meaningless.
The session ran for only the final 16 minutes of its scheduled hour because the track was too wet.
After the rain abated, seven cars set times on the ‘extreme’ wet tyre but neither title contender Lewis Hamilton nor Sebastian Vettel were among them.
Massa headed Stroll by 0.228 seconds with Renault’s Nico Hulkenberg third.
Qualifying is due to start at 13:00 BST, by which time the rain is forecasted to abate.
If the wet weather continues, qualifying could be delayed until the track is deemed suitable.
Toro Rosso’s Carlos Sainz was fourth fastest from Renault’s Jolyon Palmer, Sauber’s Marcus Ericsson and the second Toro Rosso of Daniil Kvyat.
No-one else completed a full lap.