Higher water will make a huge difference. We were already brushing 70-degree water temps some days at this point last year on the Yellowstone. Now we're running 60-63 as a daily swing and it's unlikely to increase much. It's always a race between the snowmelt and the heat. The higher the snowpack, the longer the melt, the less time we have heat and low water combined. By the time the Yellowstone at least gets low enough for the heat to really bite it, the nights will be cold even if we stay in this hot pattern.
Owner, Yellowstone Country Fly Fishing
Head Guide, Parks' Fly Shop
Fly Designer, Montana Fly Company
Author, Yellowstone Country Flies and River Characters