Sebastian Vettel said his eighth pole position of the season did not come easy after unpredictable weather made timing his best lap critical.
The German admitted that he had been initially uncomfortable with his Red Bull in Q1 but changed his approach for Q2, which enabled him to contend for pole.
"It was a difficult session all in all," he said. "Q1 and Q2 with the tricky conditions, and the circuit drying up very quickly and it being tricky on inters – the main target was to get through.
"I didn't feel comfortable right in the beginning, but in Q2 we made a big step forward. I rediscovered Spa in a way and found some better lines than all weekend and in Q3 we were quite sure it was dry [enough for dry] tires but also quite sure if it didn't rain it would be down to the last lap."
Vettel added that the lack of dry running this weekend meant he went into qualifying still learning about the car.
"I wasn't really happy yesterday or this morning, but we did the right steps to come back and especially when it was drying up. If you would put your money on that around here, all in all we got the timing right, especially in the last qualifying session it was feeling good and we got it together all the time.
"I was trying to make my way around in the last two laps [in Q3], trying to get temperature in the tires, trying to push as hard as I could. Lewis [Hamilton] was right in front of me a couple of seconds ahead and I saw him locking up, last thing. I was happy with the car toward the end in the dry and it seemed to get quicker and quicker. Not an easy session with conditions changing and right after it finished it started to change again, but here, as we saw today, anything is possible.
The World Champion said it would be impossible to predict tomorrow's race and that he hadn't ruled out more uncertain weather conditions to play a part in it.
"It is one of those races, anything can happen from start-to-finish, we will see," he said. "The best forecast around here is to look up and see what is happening!
"We had a good balance in the end in the dry, the beginning of qualifying I didn't really feel comfortable. Even in the wet we found direction and it should be ready for tomorrow, it is a long race so I am looking forward to it."