I've seen some river temps near me approach or exceed 70 degrees recently. One hit 72 and since I have no interest in keeping any trout I had to go find cooler water. Even if a fight and release is quick, fish survival is at risk in that range.
The graphic below describes the basics. Below 65 degrees and the trout are happy but get closer to 68 and they tend to get lethargic. Above that, mortality rates increase even with proper C&R.
If you're a catch-and-release trout fisherman, get to know these guidelines by heart and play by them. Measure the water temperature before making your first cast. It's tough to finally hit the river and find out you shouldn't be fishing it but do it anyway.
If you are searching for table fare, then this info may not be as impactful, but you should know that you might as well keep all the fish you catch if temps are 68+ (within regulation of course.) Releasing fish you don't want will have the same struggles.