September Fishing on the Smith River

September weather, streamflows, and summary

Similar to June, September on the Smith River is best described as two separate seasons. Early September feels more like late summer—low stream flows that make floating very difficult and water temperatures teetering on too warm for actively feeding fish. But, as the middle of September arrives things turn the corner to the positive within a few days.  

As days grow shorter, water temperatures drop to near ideal levels for trout. Around mid-September, irrigators turn off their head gates, which often results in a small but meaningful bump in streamflows. Fall trips are always a gamble on the Smith, and some years the river is still too low to effectively float. There is about a 50 percent chance that flows will be high enough to get down the river for experienced boaters for a late fall trip – it all depends on streamflows.

September weather on the Smith River can dish out heat, cold, rain, and snow. Daily high temperatures have a broad range—from 80 degrees F in early September to around 60 degrees F by month’s end. Precipitation is a little higher than August, piling up to about 1.5” and the potential for the season’s first snowfall exists towards the end of the month. Because weather is so varied in September on the Smith River, the fishing is diverse as well with opportunities for fishing large dry flies, head-hunting trout rising to Blue Winged Olive Mayflies, or targeting large brown trout with streamers. 

September fishing: what to expect

The fishing on the Smith River changes dramatically throughout the month. Because flows and water temperatures in early September are rarely conducive to great fishing, most anglers wait till the second half of the month. 

If it is even possible, fly fishing the Smith River in early September can feel like a summer day. Fish will be active before the sun is high overhead. A few fish may rise to a well-presented caddis or grasshopper.  Once the sun gets high overhead a tandem nymph rig or slowly dragged or swung streamer may entice more fish to strike than might be willing to rise to a dry fly. Choose tan or grey grasshoppers in sizes 8 to 12. For tandem nymph rigs choose beadhead Pheasant Tails or Copper Johns in sizes 14 or 16. 

After irrigators close their headgates and cease using the Smith River’s streamflows, usually by mid-September, flows increase, making floating and fishing the Smith River canyon again viable. Fishing can be terrific in late September, with lightly pressured trout looking for grasshoppers on sunny days or Blue Winged Olives on rainy or snowy days. 

For dry flies choose grasshoppers in sizes 10 or 12 and for Blue Winged Olive dry flies, choose high-floating patterns in size 16. A proven set-up for late-September on the Smith River is a size 10 Chubby Chernobyl or PMX with a size 16 beadhead Pheasant Tail as the dropper fly. This truly is a great time to enjoy some high-quality dry-fly fishing.

As the first cold front passes through—which often does occur in late September—this brings on the start of fall and brown trout begin to prepare for their spawn and become more aggressive. These larger trout actively seek out prey while also protecting their territory. For targeting the Smith River’s large brown trout on streamers, choose black or olive streamers or Wooly Buggers in sizes 4 through 8. These are best fished in and around structure such as the Smith River’s canyon walls or the drop-offs into deeper water downstream of a shelf. 

Where to find September trout on the Smith River

Early September fishes more like summer and the second half of the month will fish more like fall. Low flows and warm water temperatures limit the fishing action until the middle of the month. 

Mayfly, caddis, and stonefly nymphs are active in the Smith River year-round. In early September’s summer-like conditions of bright sunshine, trout are going to be found in subsurface holding lies. If fishing tandem nymph rigs in early September, focus on the deeper water near shallow water, behind or in front of structure, or any place that can provide cover from predators or fast currents.

Throughout September, but especially so in the middle of the month, trout will key in on terrestrials. Grasshoppers, ants, beetles, crickets, and spruce moths may land on the water. Look for trout rising to these land-based insects in any possible holding lie—pocket waters in-front, around, and behind rocks; drop-offs downstream of shelfs; along the limestone cliff walls; and along ambush-friendly bank structure. 

As the middle of the month comes and streamflows increase and water temperatures lower, hatches of Blue Winged Olive mayflies commence. When a strong hatch occurs, look for trout in slower currents and “softer water” such as the inside of river bends, seams behind rocks, and slower runs below riffles. 

After the season’s first cold front passes, look for brown trout in the usual predator hangouts—deeper water near shallow water, hiding near structure, or along a cut bank. Although most brown trout will spawn in October or November, a few browns may begin spawning in late September. They may be found on their redds on shallow gravel bars. Please avoid targeting spawning trout when they are encountered.

Important September hatches

A variety of hatches occur on the Smith River in September. However, later in September is much better than early September. Fall Blue Winged Olive (BWOs) mayflies can hatch after the first cold front passes through, typically around September 15th. A cool, slightly rainy or overcast day is ideal for a strong emergence of BWOs. These mayflies are slightly smaller than their spring season cousins. Ranging in size from 16 to 22, these insects will emerge by late-morning or early afternoon and can provide a few hours of dry fly fishing opportunities. 

Throughout the month, the weather can be warm enough for fishing terrestrials. Grasshoppers, ants, spruce moths, beetles, spiders, crickets, and any other land-dwelling insect that may inadvertently find its way into the river could end up as trout food.

Rounding out the hatches for September include a few caddis hatches in early September and the occasional early October caddis in late-September. 

Smith River fly box for September

Grasshoppers sizes 4 to 14

Crickets in sizes 8 to 12

Ants in brown, cinnamon, and black sizes 12 to 20

Beetles in black sizes 10 to 18

Spruce moths mottled in tan or grey in sizes 12 to 16

BWO dry flies sizes 16 to 22

BWO emergers sizes 16 to 20

BWO nymphs sizes 16 to 20

Stonefly nymphs in brown and black sizes 4 to 10

Caddis pupae sizes 14 to 16

Caddis CDC emergers sizes 14 to 16

Caddis dry flies with dark grey, black or brown bodies sizes 14 and 16; 

October caddis size 8

Crayfish patterns sizes 2 to 8

Sculpin patterns sizes 2 to 6

Streamers in olive, black or brown sizes 2 to 6