Boulder River Fishing Report

This Boulder River fishing report is valid from May 23, 2025 until roughly June 15, 2025.

The Boulder is clear and in good condition as I type this, but warm weather in the forecast means it will blow out again in a few days and rise to maximum spring runoff. Keep a very close eye on the stream gauge below. Anytime the water is on the drop and below 2500cfs, it’s worth float-fishing if you’re good on the sticks. Flows below about 1500 are wadeable.

While it’s clear, fish streamers and stonefly and attractor nymphs in the larger, slower runs.

• Hatches: Mother’s Day Caddis (limited).
• Dry Flies: Large caddis-style attractor dries, such as #12 Coachman Trudes and Clacka Caddis.
• Nymphs & Wets: #4-10 stonefly nymphs (Girdle Bug, Minch Stone, 20-Incher, etc.) either in combination or trailing a big San Juan Worm or a #10-12 attractor  nymph like a Prince or Bead, Hare, and Copper. You can even throw on something like a Woolly Worm with current conditions.
• Streamers: Black or white Woolly Buggers or Bow River Buggers (Woolly Buggers with Muddler heads) and similar bulky junk flies, #2-6. The clearer the water, the more likely olive, tan, and other natural colors are worth a shot.

Learn more about fishing the Boulder.

Learn more about our float trips, including on the Boulder.

Boulder River Streamflow Data

This stream gauge is near Big Timber, right at the bottom of the Boulder near its confluence with the Yellowstone. The Boulder actually runs slightly higher near the Boulder Forks Fishing Access, since a great deal of water is pulled off for irrigation downstream. Further upstream, the Boulder is much smaller, since the East and West Boulder both come in near Boulder Forks.

Flows under 500cfs are fishable on foot, 500-1500 both on foot and floating, and 1500 to 2500 only floating.

Boulder River Fishing Report – Relevant Links

• Mcleod Weather

Note: We update our general fishing report far more often than our fishery-specific reports like this one, especially between November and April.