Richard Tate

Fly-fishermen know that their summer outings are often limited to certain streams and stream sections that remain cold enough to host trout throughout even the hottest of weather. 
Some of these are the well-known limestone spring creeks of southern Pennsylvania, such as the renowned LeTort Spring Run and Falling Spring Branch. Tactics on these waters include nymph fishing for trout, dry-fly fishing with terrestrial insect imitations, and fishing to hatches of tricorythodes mayflies where they can still be found. 

By autumn, most sportsmen from Pennsylvania and other states across the country are focused on the hunting seasons. This is especially true of deer hunters who hunt with bows and crossbows.  
Only a few sportsmen are interested in fly-fishing for trout; but the ones who are have the chance to make fine catches while fishing uncrowded streams.
The best autumn fly-fishing begins close to the first day of autumn. By that time trout streams that may have been too warm for trout have cooled off to temperatures that trout find tolerable.