The active temperature range for trout.

Trout are most active and likely to be feeding in water that ranges from 40 degrees to 60 degrees F.  If the water is colder or hotter, the trout become lethargic, sluggish or dormant.  And, they become much harder to entice with your flies.

In the Summer of ’07, Montana experienced an extended period of temperatures in the high 90’s and even 100’s which caused the river and lake temperatures to rise above 70 degrees causing restrictions and closures.  When the water get too hot, trout will become less active and slow down in feeding.

The warmer water contains less oxygen for the trout and causes them to be less active.  You won’t find trout feeding on the surface with temperatures outside the “active range”.  During these times, trout move to areas where there is more aeration such as below waterfalls, riffles, rapids and run outs.  The aeration provides more oxygen and helps make the trout more comfortable.  So if it’s hot

and you want to catch more trout, here’s what you can do.  Cast your fly where the trout lie. Hit the riffles, run outs and rapids and also areas where the wind is whipping across the surface.

Another thing to try is a sinking tip fly line.  The mistake I made fishing the upper Yellowstone this summer was using a floating fly line the entire time.  A sinking tip allows you to get your nymph dropper deeper – where the trout are when it’s hot.

Lesson learned:  fish during the active temperature range for trout which is normally in the spring or fall depending on the location so you can be assured of the right combination of water temperature and rich oxygenation.  Get your fly close and deep by fishing the right areas and right depth.