The folks on the Texas Fishing Forum seem to agree with me about at least one thing. That the fishing for stocked rainbows on the fly gets somewhat slack after the air temp rises above 55 degrees. I realize water temps are slow to change generally, compared with air temps, but for whatever reason it's been my experience that the chillier it is, the friskier and hungrier the trout are.
I have not done a great deal of reading about trout in terms of their physiology and I know our stocked trout are raised in Texas hatcheries. I suspect the water temp is keep cool there, relatively speaking, since to survive during 100 degree plus days requires some cool water.
I figure that these hatchery trout just have an innate and inborn and genetic liking for the chillier temps, and their nature kicks in when it's say 30 degrees outside and something tells them to hit that fly or nymph because it's food but when it's 70 degrees air temp that same fly doesn't seem worth the effort to rise and pursue.
Some interesting recommendations over at the Texas Fishing Forum in terms of flies to use, and I'll list a few in case you don't want to make the jump. One of the posters on that thread, or at least one, seems to have a lot of knowledge about Texas trout fishing as I've read many of his posts and think he's knowledgeable.
This fellow recommends a beadhead or cone head woolly bugger (booger?) in olive or black for topwater and a small, dark beadhead nymph below. Another poster at the site recommends a PMD parachute and a black midge dropper in black and olive, as well as an Elk Hair Caddis with a black dubbed body.
I myself have had great luck with black midge and dark nymph patterns as well as, believe it or not, small Dave's Hopper flies. This is in spite of the fact that grasshopper season is long gone by the time trout stocking happens. In any event, maybe some grasshoppers hit the hatcheries when the fish are small and they see them. I just know that the Dave's Hopper has caught trout for me in Texas in winter.
On another thread at the forum, one fellow mentions that the springs are 80% down on McKittrick Creek in the Guadalupe Mountains. That's the home of the other trout population that survives year round in Texas, the other being the Guadalupe River below Canyon Dam.
The poster mentions he went on a hike with National Park folks to that creek earlier this month and reports on the greatly diminished output of the springs there due to our on-going Texas drought. The National Park forbids fishing in McKittrick Creek for the now native born rainbows (from rainbows stocked there years ago before the Government bought the land) and they flourish with literally no natural predators and the cool water in the high mountains.
It's a shame that McKittrick Creek is having a hard time, but much of West Texas and lots of the Hill Country and other parts of Texas have yet to recover or fully recover from the effects of the bad drought of 2011. This year held some promise early on, with some rain, but we haven't had near enough rain to fill our rivers and more importantly lakes and recharge our aquifers to give flow to the springs.
Our area has water, but it wouldn't take much to put us back on severe water restrictions, as we've had the past two summers. It was sort of like a Seattle day around here the past couple of days, not really rainy but just drizzly all day long. Better than nothing.