With the mayflies try matching the hatch with the appropriate CDC emerger, comparaemerger, comparadun, or comparaspinner. Fish the areas of moving water as the slow pools can get difficult. The lower stretches can get warm on sunny days. Floating can mean a lot of dragging too. Look for fish in the tails of riffs and in the deeper stretches of pools.
Lower stretches can warm up on hot, sunny, summer days.
The whole river stays cool and usually fishes nicely. Look for active fish throughout the river system. There is plenty of water to float and you can wade the river nearly everywhere. At this level look for fish out of the main current. At this level floating comes into its own.