I don't know from first hand experience, but according to the USGS, it looks like it'll start getting good in October, and some years stays good through february/march.
The flows should start a very gradual decline right about this time of year and will continue to drop as water demand decreases mainly from the farmers, untill the flows bottom out around December.Fishing remains good as the flows decrease you just have to move around and find where the fish are at.