Mark Webber clinched pole position for Sunday's Belgian Grand Prix in a rain-affected qualifying session.
The Australian took his fifth pole of the season with his first effort in Q3, before light rain towards the end of the final shootout hindered all attempts to beat him.
Lewis Hamilton managed a lap good enough for a place on the front row, despite finding La Source hairpin wet at the beginning of it.
Fernando Alonso was also on track trying to improve at the end after a poor first lap on the harder tire - he was the only front runner not to go straight out on the soft. But on his second effort he lost significant time at the damp La Source and posted a time 1.6sec slower than Hamilton, only good enough for 10th.
Robert Kubica and Sebastian Vettel will share the second row of the grid, both setting their quickest times on the session's first run.Like team-mate Hamilton, Jenson Button was able to improve despite the rain at the end to push Felipe Massa down to sixth.
Rubens Barrichello will start seventh, as he celebrates his 300th grand prix, alongside Force India's Adrian Sutil. Nico Hulkenberg heads Alonso on row five.
The Mercedes of Michael Schumacher and Nico Rosberg - who will each take a grid penalty anyway - finished qualifying in 11th and 12th after they were relegated from Q2 by the two Williams at the very end.
The fastest Q2 times were set right at the end as the track dried throughout. The McLarens of Hamilton and Button were the only cars to break into the 1m46s, while late efforts from Vettel and Webber put them third and fourth and guaranteed safe passage to Q3. Sutil, Massa and Alonso survived trips off the road early in Q2 to book their place in the final segment.
Jaime Alguersuari, Vitantonio Liuzzi and Sebastien Buemi were eliminated, while Heikki Kovalainen pipped Timo Glock to quickest of the new cars in 16th.
There was chaos back in Q1, triggered by Renault's Vitaly Petrov. The session started dry but with dark clouds rolling in, so all 20 cars took to the track straight away to get a time in before it rained.
But Petrov dropped it at the Turn 9 left-hander and spun back into the barrier on the inside. The resulting red flag period delayed things just long enough for a deluge to hit Rivage and Stavelot on the first flying lap. Lucas di Grassi, Adrian Sutil and Jarno Trulli all went off at Stavelot, while the McLarens of Hamilton and Button left themselves enough clear track to go straight to the top of the timesheet. Vettel had waited in the pits for 45 seconds longer than everyone else and was only 17th - the circuit much wetter by the time he completed his lap.
But the track dried in the next 10 minutes, allowing both Mercedes and both Williams to leap into the top five on slicks right at the end. The Saubers of Kamui Kobayashi and Pedro de la Rosa also went out on slicks hoping to jump up into Q2, but slid off the road at Rivage and Stavelot respectively and both went out.
Di Grassi and Petrov were unable to post times after their incidents, and were joined by Sakon Yamamoto, Bruno Senna and Trulli in being eliminated in Q1.
Pos Driver Team Q1 Q2 Q3
1. Webber Red Bull-Renault 1m57.352s 1m47.253s 1m45.778s
2. Hamilton McLaren-Mercedes 1m56.706s 1m46.211s 1m45.863s
3. Kubica Renault 1m56.041s 1m47.320s 1m46.100s
4. Vettel Red Bull-Renault 1m58.487s 1m47.245s 1m46.127s
5. Button McLaren-Mercedes 1m57.981s 1m46.790s 1m46.206s
6. Massa Ferrari 1m58.323s 1m47.322s 1m46.314s
7. Barrichello Williams-Cosworth 1m55.757s 1m47.797s 1m46.602s
8. Sutil Force India-Mercedes 1m58.730s 1m47.292s 1m46.659s
9. Hulkenberg Williams-Cosworth 1m55.442s 1m47.821s 1m47.053s
10. Alonso Ferrari 1m57.023s 1m47.544s 1m47.441s
11. Schumacher Mercedes 1m56.313s 1m47.874s
12. Rosberg Mercedes 1m54.826s 1m47.885s
13. Alguersuari Toro Rosso-Ferrari 1m58.944s 1m48.267s
14. Liuzzi Force India-Mercedes 2m01.102s 1m48.680s
15. Buemi Toro Rosso-Ferrari 2m00.386s 1m49.209s
16. Kovalainen Lotus-Cosworth 2m01.343s 1m50.980s
17. Glock Virgin-Cosworth 2m01.316s 1m52.049s
18. Trulli Lotus-Cosworth 2m01.491s
19. Kobayashi Sauber-Ferrari 2m02.284s
20. Senna HRT-Cosworth 2m03.612s
21. Yamamoto HRT-Cosworth 2m03.941s
22. de la Rosa Sauber-Ferrari 2m05.294s
23. di Grassi Virgin-Cosworth 2m18.754s
24. Petrov Renault no time