Paul di Resta qualified in fifth and the British driver looked set for an upset until the drivers came back out on new tires.
Last year’s winner Jenson Button starts from sixth for McLaren, ahead of Lotus pair Kimi Raikkonen and Romain Grosjean. But it was a bad afternoon for Fernando Alonso, who was ninth for Ferrari _ which has struggled in qualifying all season.
“The aim is to win. Anything can happen here,” a defiant Alonso said. “If we manage to pass people in front, we have the pace.”
Alonso was fastest in the first qualifying run ahead of Hamilton, with Dutchman Giedo van der Garde a surprising third.
Raikkonen topped Q2 ahead of Alonso.
The rain returned for Q3 and up went the umbrellas around the 7.004-kilometer (4.352-mile) circuit _ the longest on the F1 calendar and most difficult along with Monaco.
Di Resta gambled on some parts of the track keeping dry because the unique microclimate in Spa means it can be wet and dry in different places. He stayed out while all the others funneled back in single file to switch to intermediates.
“I saw umbrellas coming up so I made the right choice,” he said. “It was the right time, but our car is not that quick in the wet.”
The unpredictable and rapidly changing conditions caused tension.
“I think I aged about 10 years,” Red Bull team principal Christian Horner said. “The boys did a tremendous job to turn around both cars and get them out in time.”