September Fly Fishing on the Thompson River

Last September, fall rains brought a welcomed end to the stale, smoky air which darkened the days since mid-August. Since sitting in a camper with two dogs while it rains is not appealing, instead, we spent rain days exploring.

We were camped along the Clark Fork River just east of St Regis, Montana. Earlier in the week, we caught lots of cutthroats, rainbows, and browns in the Clark Fork.

We opened the atlas and looked for nearby blue lines. The Thompson River would be our target.

Tributary of the Clark Fork River

The Thompson River is a tributary of the Clark Fork and joins the Pacific-bound waterway near Thompson Falls, Montana. Thompson River Road, a good gravel road, follows the river closely for much of its 43 miles.

Signs, as you enter the area, warn that bull trout must be immediately released, however, only the water in the last mile before the confluence with the Clark Fork looked interesting enough for bull trout.

Access to the River

Access to the Thomspon is ample. Both the Thompson River Road lies to the west of the stream while the ACM Road lies to the east. For such a small waterway, it’s a little strange to have a road on each side. But this area is a big timber area and the roads were built to access vast tracts of forest.

Numerous primitive campsites dot the streambank and make perfect access points for fishing as well as picnicking or camping.

On that rainy Saturday, we drove along the river, first on the westside road, then near the 17-mile marker, crossed a bridge, and returned on the ACM road, making note of places to try when the weather improved. We were impressed with the small river and were excited to return.

Cutthroat trout in the Thompson River

Thompson River Cutthroat

Fishing the Thompson River in September for trout

September Fly Fishing

Deep Pools and Hungry Trout

On our return, we headed for a spot we had noted – a big bend pool. It took just one fly change to net the first cutthroat. I fished a CDC Caddis with a small pheasant tail nymph trailer.

The fish were all small, 6 to 12 inches. Strikes were aggressive and the fight on a lightweight fly rod was fun. The trout were not fussy, several patterns bought fish to the net.

This was the perfect side-trip. We returned a second day as the scenery and the trout were just delightful.


The Thompson River has several notable hatches. Caddis are an important food source that begins hatching in May with hatches through September. Other notable hatches include salmonfly, baetis, and midges. Terrestrials are an important food source and include grasshoppers and flying ants.

Things To Know If You Go

Cell service ends just a mile or so up the Thompson River Road. The valley is very tight and the mountains are rugged that line the canyon. Thompson River Road connects two main thoroughfares in Montana; Route 200 which follows the Clark Fork and Route 2 between Kalispell and Libby.

The nearest town for services and shopping is Thompson Falls. The lower river has the better fishing due to its size. The upper portion is small with even smaller trout.

The streamside campsites are free and first-come, first-serve.

A weekend here is perfect. For us, the Thompson was a side trip in a larger fishing trip.

Fishing regulations for the Thompson River in Montana

Fishing regulations for the Thompson River

Fishing the Thompson River in Montana

Thompson River Map

Cutthroat Trout from the Thompson River

Caddis Eater

A Deep Run in the Thompson River

Tim Fishing a Deep Run

Local Experts

Bring flies with you when you come as there are no local shops. The closest shops would be Joe Cantrell’s in St Regis. He also gives updates on the Thompson.

Flies That Worked For Us

Here’s what we used during our trip on September 18, 2020

  • CDC Caddis (gray and olive)
  • Elk Hair Caddis
  • Pheasant Tail Nymph
  • Foam Hopper
  • Griffiths Gnat
  • Size 20 BWO Parachutes
USGS Water-data graph for Thompson River in Montana

Nearby Fly Fishing Waters

There are ample fishing opportunities in Northwest Montana

  • Clark Fork River
  • Kootenai River
  • St Regis River

Thompson River Photos

Fishing Guidebooks

Go with knowledge! We keep guidebooks in the camper and the state atlas in all of our rigs. If you’re serious about fishing, here’s our recommended reading for this water.

*The link takes you to Amazon where you can read more about the titles and purchase the guidebooks if you choose. We do receive a small portion of the sale for providing the link which helps to support this site. We appreciate your support!

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