Lets not forget that it rained in Q2. The track wouldve been drying in Q3, thus each passing driver wouldve been making the track greener so to speak.
I thought it rained at the end of Q1. Alonso was first out in Q2 and it had stopped raining for at least 5 mins by then. It would have been dry for the start of Q3 easily.
Also didn't someone go out at the end of Q1 and set an improved time? That was the impression Steve Ryder gave in the break between Q1 and Q2. If so it can't have rained that hard.