Good question Casey. I'd think that if we have a sunny weekend, the hike will be hot, given the location and terrain, so the water should feel good, even if it is cooler than in July. How cold was the water in July? Cool or cold ( like Pine Falls, brrr).
As far as Poison Oak, in full bloom does not make it any larger or more intrusive than later on. It may be all shiny now, but it will only grow larger from here on.