Its normal for it to slow down around that time, especially with bright sun. Fish do not have eyelids so the sun affects them.
What I do is concentrate on real heavy/fast water, where the suns rays are broken up and do not penetrate through the water column as well. Also, look for shady areas. I believe that the trout really seek these types of zones out during the conditions that you described.
Give it a try and let me know!