This time of year depending on the weather there may be lots of opportunities for dry fly fishing. In addition to the BWOs, callibaetis, March Browns and some stoneflies may also be hatching. These hatches can be quite prolific but most often the number of rising fish is sparse. As noted in a previous post, finding the water holding rising fish is of utmost importance. The water upstream from the Rush Creek launch area to the bridge in Lewiston can hold rising fish.
This time of year the fish could be steelhead smolts, quarter pounders (12-15"

, half pounders (15-20"

, some hatchery fish, and a couple of populations of late run wild fish (2 to 3 pounders and 5 to 7 pounders). These fish at times can be caught on dries.
There may be a few browns as well. The browns are more likely to eat streamers than dry flies. There are big browns in the river (over ten lbs) but these move around and are harder to find. DFG studies have found that the largest concentration of browns are around the islands at Poker Bar and in the area around Indian Creek. There is a lot of water to explore so just hit the public access points and keep moving untill you find fish. This time of year the middle of the day is the best time to fish with dries.