The temperature in the Yampa River at noon Friday was 67 degrees, and don't think the trout in the river's town section failed to notice.
River temperatures had poked into the 70s the preceding week, a range in which trout become less active.
But the trend reversed itself after an intense monsoon thunderstorm crashed into the valley Monday. The storm bumped streamflows higher Tuesday morning and brought temporary relief from the warm water. But the brief flirtation with a monsoon pattern also brought a more lasting change to the valley's weather patterns. It would be premature to say there is a touch of fall in the air, but overnight temperatures consistently dipped into the 40s throughout last week.
The result was river temperatures that were more favorable for trout and some of the best late-summer fishing along the town stretch of the Yampa River in four years.
The Yampa was flowing at 147 cubic feet per second Friday at the Fifth Street Bridge. That's nearly three times the typical flow on that date for the previous three years. The U.S. Geological Service no longer takes daily temperature readings at the Fifth Street Bridge. However, an unofficial reading at a flowing-water depth of about 1 foot Friday produced a tempertature reading in the high 60s.
Area experts said fish are feeding heavily on caddis flies and caddis larva. But in some sections of the river, they are taking dark-colored mayflies throughout the day in the pocket water behind boulders.
Jaret Duty of Bucking Rainbow Outfitters said that shortly after the heavy rainstorm, San Juan worm patterns were rewarding fly fishers. The rain washes a variety of feed into the river, and for a time, the local trout population was seeing a lot of annelids coming into the main stem of the Yampa from its various tributaries.
Even during the preceding week, when water temperatures were warmer, trout in the pocket waters were looking for mayflies, Duty said. And the fish weren't particularly fussy. A standard Adams pattern was a reasonable choice to match the hatch, but the trout were willing to strike at any dry fly.
Sam Spillane at Steamboat Flyfisher said he's begun to notice the early signs of the annual trico hatch in the mornings. Anglers who want to key in on this action might try patterns that imitate drowned adult mayflies in size tiny.
The good news is that anglers who don't want to get that technical can do well with the hopper/dropper system, tying hare's ears nymphs size 16 to 18 beneath a highly floatable grasshopper pattern.
Caddis hatches still are going strong about an hour before sunset, Spillane said. If it looks like the fish are keying on emergers, consider fishing with unweighted hare's ears or pheasant-tail nymphs.