Today the temperature is supposed to reach almost 100 degrees. Great for those beach goers but not so much for us fishermen. When the days are really hot and the nights are really warm, the water temperatures starts to climb and when the water temperatures start getting closer to 70 degrees it stresses the fish. Trout and salmon in particular. So even though they swim away after you release them most likely the will die due to the higher water temperatures.
Typically I switch my target fish to smallmouth bass from the end of July to second week of September when nights start to cool down. Bass can handle the warmer water and seem more resilient. They will seek fast oxygenated water to stay cool. This time of year they are typically feeding on hoppers, dobson flies or adult stones that hatch at night. So I throw poppers, hoppers or Chenobly ants, in multiple colors.
Something to keep in mind, spring fed brooks typically are ice cold so if you feel it necessary to fish for trout in these hotter temps, seek out these brooks. The fish will be much smaller but still worth dropping that fly for. I use my Scott fiberglass 7 foot, 3 weight or 2 weight. Those little trout will really bend the rod and make it fun. If you want a shot at a bigger fish, try fishing early morning or later in the evening when temperatures drop. Try to keep the fight short and sweet, the fish in the water and release the fish as quickly as possible!
I hope this give you something to think about on your next fishing trip!