Red Bull's Max Verstappen and Sergio Perez led the field in the third and final practice at Spa, a session held in changing but mainly damp conditions.
Verstappen edged his teammate by 0.947s while Mercedes' Lewis Hamilton was over a second adrift from the Dutchman.
Behind the leading trio, McLaren's Lando Norris and Alpine's Esteban Ocon rounded off the top five.
Despite the bleak forecasts, drivers were spared full wet sessions on Friday, but the dark clouds were hovering once again over Spa on Saturday morning, with a shower dampening the track ahead of FP3.
The field thus headed out for its final dress rehearsal shod with Pirelli's intermediates, save for Haas' duo which opted for full wets.
Williams' George Russell was the first driver to post a flyer, but the Briton's time was quickly bettered by AlphaTauri's Pierre Gasly, but drivers were working overtime in the relatively precarious conditions.
Fifteen minutes in, Hamilton sprung to the top, but as a dry line appeared to emerge Verstappen clocked in a full second faster than his title rival, setting the benchmark at 1m56.924s.
The Dutchman's freshly re-signed Red Bull teammate, Sergio Perez, slotted in second, heading among the top five Hamilton, Lando Norris and Esteban Ocon.
But with 30 minutes left on the clock, a burst of light rain reduced the dry lines, leaving little room for improvements.
However, with a wet race on the cards for Sunday, many drivers remained on the track, gathering data, save for Verstappen in the Red Bull camp who saw little point in pounding around the wet track and decided to bring his session to a premature end.
Others continued to tour around on inters, but Gasly indulged in a harmless spin on the exit of Turn 14.
Over at McLaren, Norris bravely bolted on a set of slicks, perhaps to test the cross over point from wets to slicks for Sunday, but the Briton looked like Bambi on ice during his tricky single lap.
The session eventually concluded with Verstappen and Perez sitting atop the unchanged timesheet, with Hamilton third fastest ahead of Norris, Ocon, Stroll, Gasly Vettel, Russell and Alonso who rounded off the top ten.
This afternoon's qualifying is currently predicted to take place on a wet track, but Spa's ever-changing conditions will likely see the grid-defining session basking in more drama.
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