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39-acre lake in Carbon County, Montana. The lake tops out around 80 ft. The depth chart is built from real state fisheries GPS surveys, so the humps, channels and drop-offs you see are measured, not guessed. What the data behind the map says about each species, season by season:
Drawn out, this is 42 acres of water rimmed by 1.3 miles of bank. The shoreline is moderately structured (index 1.5) — enough points and pockets to pattern. The shallow band under 15 ft claims about 17% of the surface — that's where the groceries are. End to end it runs roughly 0.5 mi, about 0.2 mi across. You'll find it in Carbon County. The nearest mapped water is Varve Lake (Forsaken Lake), 1 mi to the north.
When the water first warms, cutthroat trout slide up into 3 to 15 ft. By summer they slide out to 10 to 35 ft, and by winter most fish are in 10 to 40 ft. If you only fish one area, make it Main-lake point: a point around 15 ft that scores prime in fall. In summer the feeding windows fall in early morning and the evening. Keep a trolled spoon (small) or an inline spinner rigged through the warm months.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 15 ft | dawn & dusk | Main-lake point (15 ft) | Inline spinner (silver/gold), Small spoon |
| Summer | 10 to 35 ft | dawn & dusk | Main-lake point (15 ft) | Trolled spoon (small), Inline spinner |
| Fall | 5 to 25 ft | dawn & dusk | Main-lake point (15 ft) | Casting spoon, Inline spinner |
| Winter | 10 to 40 ft | dawn | Main-lake point (15 ft) | Small jigging spoon, Marabou jig |
Structure-wise the chart holds 5 features, led in depth by Deep basin at roughly 80 ft.
Season dates, license requirements, and size and bag limits for Montana waters are set by the Montana Fish, Wildlife & Parks — and special regulations can apply to Flat Rock Lake specifically, so confirm the current rules before you fish.
Check the official Montana fishing regulations →
Flat Rock Lake is about 80 ft (24 m) deep at its deepest point. The depth chart here comes from real state fisheries GPS surveys, so the contours reflect measured depths.
Anglers target cutthroat trout on Flat Rock Lake.
Main-lake point is the top-rated area: a point in about 15 ft of water that rates prime for cutthroat trout in fall. The interactive chart above rates every spot for each species and season.
For cutthroat trout, the summer bite is best in early morning and the evening. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Fishing on Flat Rock Lake is regulated by the Montana Fish, Wildlife & Parks. Check the official Montana regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Varve Lake (Forsaken Lake) 1 mi · Crystal Lake (Carbon) 1 mi · Castle Lake 1 mi · Donelson Lake 2 mi · Erratic Lake (Carbon) 2 mi · Two Bits Lake 2 mi · Till Lake 2 mi · Cloverleaf Lake #216 2 mi · Cloverleaf Lake #215 3 mi · Green Lake (Carbon) 3 mi · Cloverleaf Lake #223 3 mi · Estelle Lake (Carbon) 3 mi
See how Flat Rock Lake stacks up: best cutthroat trout lakes in Montana
More water nearby: Carbon County fishing maps (65 charts). Browse all Montana fishing maps or see every water on DepthScout. Bathymetry credit: state fisheries survey programs. How we build these maps. Fish here with a sonar unit that logs? Send us your depth data and we'll improve this chart, credited to you. For fishing guidance only, never navigation.