Anglers often ask what the best time of the day to fish is and often my answer is well really anytime of the day you can be on the water. All jokes aside there are certainly "optimum" hours during the day that fish are most active and feeding. One the most consistent times no matter the season is the evening.
During the summer months the sun is high, when evening time arrives the sun dips and fish become a little less weary of overhead predators and hatches of caddis, pale evening duns, or spinner falls bring fish up to the surface. Summer evening fishing can keep anglers well into the fading light as fish stay active into the darkness.
As the summer months transition to fall and winter, daytime temps warm the water all afternoon making the evening water as warm as it can possibly get. During the final hour of daylight often times "the bite" can pick up. Perhaps it's the warmer temperatures, perhaps it's last call before night hits and fish go a on a quick binge. This exact thing happened on a recent trip to Montana. Fishing on the Madison and Missouri during the day was so-so, finding a random fish here and there, then as the light settled there seemed to be a burst of action and the short lived flurry capped off the day with some nice fish.
Same thing goes for steelhead fishing. Many folks quit while there is still plenty of light on the water and miss out on that one-last-opportunity fish. Back when I guided the Grande Ronde I would often fish clients up to the last minutes of daylight then row out the final stretch of river in the dark. While that would make for some long days it also usually added to the fish count. And in steelhead land where fisherman report how many "grabs" they got... you better damn well bet we were gunna optimize every minute of light we could.
Whatever season it may be, the evening seems to be a special time of the day where fish loose some inhibition and feed a little less cautiously. Big fish that may have laid low during the bright sun go on the prowl for an evening meal, insect life is a little more active, wind tends to lay down a bit (unless you fish the Madison River where it never does), and overall there seems to be a tranquil hour of good fishing that is always worth staying out for.