Updated October 15, 2026
    Access point

    Harriman State Park / Falls Areaon Henry's Fork (Upper Henrys Fork)

    Classic dry-fly water with runs, tailouts and good public access through Harriman State Park.

    River flow last 30 days

    04008001,2001,600Sep 16Sep 22Sep 27184 cfs
    Flow now
    92cfs
    Below the typical range (241–697 cfs)
    Last 7 days
    Steady
    184 to 373 cfs
    Weather now
    58°F
    Clear Sky, wind 8 mph SW
    Bite report · week of Oct 4

    Good fishing conditions on the Upper Henry's Fork

    Tactical tipSwitch to streamers during cloudy conditions to entice aggressive predatory trout.
    1. 01Good fishing conditions on the Upper Henry's Fork, favoring nymphing, dry-dropper, and streamer tactics.
    2. 02Expect active hatches of Mahogany Duns, Blue-Winged Olives (BWOs), and Pale Morning Duns (PMDs).
    3. 03Top fly recommendations include Mahogany Dun, BWO Comparadun, PMD (dries), Flashback Pheasant Tail, Copper John, Zebra Midge (nymphs), and Olive Woolly Bugger, Pine Squirrel Leech (streamers).
    4. 04Focus efforts on the Upper Henry's Fork above Ashton, targeting deeper runs and riffles, but also slower sections for rising fish.

    What to tie on at Harriman State Park / Falls Area

    Picked from recent reports for this stretch.

    dry80%

    Blue-Winged Olive Comparadun

    #18#20#22

    BWOs are actively hatching in the fall, especially on overcast days, and this low-profile dry fly is excellent for selective trout.

    Buy at Amazon
    dry80%

    PMD (Pale Morning Duns)

    #16#18

    Pale Morning Duns are actively hatching in fall, providing a key food source for opportunistic feeders on the Henry's Fork.

    streamer80%

    Pine Squirrel Leech (Olive)

    #14#16

    Small leech patterns like this effectively mimic sluggish baitfish and annelids in cold water, triggering strikes from larger, lethargic trout in the fall on the Henry's Fork.

    nymph80%

    Flashback Pheasant Tail

    #14#16#18#20

    An excellent general searching nymph, mimicking various aquatic insects active subsurface year-round, and particularly effective in fall conditions on the Henry's Fork.

    nymph80%

    Copper John

    #14#16#18

    A versatile attractor nymph, effective year-round in faster water, ideal for prospecting deeper runs where fish are holding in cooler fall temperatures on the Henry's Fork.

    Buy at Amazon
    nymph80%

    Zebra Midge

    #18#20#22#24

    The most consistent winter producer on the Henry's Fork. Black or red in sizes 20-22 mimics the prolific midge larvae present in the substrate year-round.

    Buy at Amazon
    dry80%

    Blue-Winged Olive Comparadun

    #18#20#22

    Blue-Winged Olive hatches are active in early spring, especially on overcast days like today, and this low-profile dry fly is excellent for selective trout feeding on emergers and adults.

    Buy at Amazon
    dry80%

    Mother's Day Caddis

    #14#16#18

    The prolific Mother's Day Caddis hatch is expected in late April through May on Western rivers, making this dry fly a perfect imitation for adult caddis.

    nymph80%

    Flashback Pheasant Tail Nymph

    #14#16#18

    An excellent general searching nymph for early spring, mimicking various mayfly nymphs (including BWOs) that are active year-round and particularly as BWOs begin to emerge.

    Idaho season by season

    What changes on the water through the year, with the flies for each season.

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