Water temperature for fly fishing for trout.
If you want to be really knowledgeable about trout fly fishing, you should be looking at a range of factors which include, water temperature, clarity, the presence of plant life, and so on.
In terms of oxygen quality, though trout prefer high concentrations of Oxygen, 8 parts per million (ppm) O2 is good but at levels lower than 5ppm fish are expend all their energy moving their gills and trying to breathe. As a result of lower levels of oxygen they will quite understandably move to an area with more oxygen.
In a stream trout will move into riffles, runs and eddies: places where oxygen is mixed into the water by the air.
In a lake they may change depth or seek out the water around inlets or areas where wind and current stir surface. Heavy rain will cool and oxygenate the water. If they cannot find relief they will die: to be comfortable they require at least 5ppm of oxygen. Oxygen at high levels makes the fish active and avid feeders and they will hit a fly with great enthusiasm.
In summer in bright, warm conditions plankton in lakes and reservoirs moves up and down in the water depending on the height of the sun and fish will tend to move down in the water with this plankton as the sun rays become more intense.
Fly fishing for trout can be just for fun and relaxation, but with the right knowledge it becomes a real art.