My biggest concern with wet wading is tick exposure. I usually wear waders, even in Summer, on small brushy streams, but if I do wet wade on a really hot day I wear quick dry long pants too.
I'll wear swim shorts on a big river like the Susky or the J where I'm either in the water all day, or on exposed gravel bars within the stream banks.
You can still get bacterial skin infections while wearing waders, and I'm not convinced the chances are all that reduced by wearing them. Waders generate a ton of bacteria, especially hot, sweaty, leaky ones. Either way the relative risk is low. Think of all the people who swim in PA lakes and streams each year (not just anglers) versus the number of infections reported. That's a risk I'm willing to tolerate given my hobby.
I see the risk of tick borne illness as much higher and a more significant reason to wear waders.
FWIW - I was just in Colorado for two weeks. Everyone, literally everyone, wet wades out there in Summer. My fiancé and I were the only two I saw in waders the whole time we were out there.
To answer the OP: Yes, that's too cold. I would have worn waders in that scenario just from a comfort perspective. Very large huevos on those guys apparently, though probably subject to the usual shrinkage factor if they dunked them in that water.
