Just like trout, there are optimum water temperatures where bass feed more actively. I was telling a friend earlier this summer that the water during our nasty, extended hot spell was too hot to fly fish - even for bass. That came as a surprise to him as he was under the misguided notion that I used to be - that bass will feed well in even the hottest of stream temps. Well, no just like any fish they have temps that will speed up their metabolism.
Smallmouth bass metabolisms perform at their highest in water temps that range from 67 degrees F to about 71 degrees. Optimum temps for largemouth bass tend to be in the neighborhood of 65 to 78 degrees. Of course, you should take these temps with a grain of salt. Bass that live down south in hotter water temps will naturally be conditioned to those higher temps & will feed actively even when the water is in the 80's. Up north, (like me here in PA) not so much. Some studies have shown that when the water gets to 50 degrees or lower, smallmouth bass 12 inches or smaller will stop feeding.
When the water gets too hot for bass, they will move to find cooler waters. This can also mean shallower water, too - in the shade. Bass love the shade all times of the year.
You'll find smallmouth bass in places where the bottom is rocky, sandy, or has a lot of gravel. Largemouth bass will also be in those places, too but you can also find them where the bottom is muddy or silty. Smallmouth require fresher, cleaner water - more so than largemouths who can take dirtier water & can even live in coastal streams.
It's a good idea to fish for any bass around structures - weed beds, sunken logs, large rocks, & underwater rock shelves. They love to sit quietly & ambush their pray.
Pound for pound bass are some of the most fun you can have at the end of your fly line!