A day on the Yakima - but when?

I've been promised a day's float on the Yakima River; time of my choice. I've fished there many times, but living 200 miles away, it's an occasional thing with me, and I'm not attuned to the seasonal rythyms of that stream. What month of the year would you pick?
I agree August is nice, especially if you don't have to row. Warm weather and big bugs is hard to beat. That said, don't rule out October. No more recreational floaters, the flows are down and the fishing can be very good. Either way, you should have a great day ... enjoy.
October is my favorite time on the Yak as well, however its also very enjoyable to wade then. If you have a chance to take advantage of a boat, do it in the summer when the flows are high and wading is difficult/impossible. I floated it last year in late July and had a great time.