What is the deepest lake in Montana?

Of the lakes with a published depth, Hungry Horse Reservoir is the deepest at about 500 ft.

Deepest lakes in Montana: 10 lakes ranked by depth

The deepest lakes in Montana with a published depth, deepest first. Deep lakes stay cold below the surface all summer, which is what trout and big predators want.

Deepest first

#	Lake	Deepest	Size
1	Hungry Horse Reservoir	about 500 ft	23,600 acres
2	Tally Lake	about 492 ft	1,330 acres
3	Lake McDonald	about 472 ft	6,820 acres
4	Flathead Lake	about 371 ft	126,000 acres
5	Lake Koocanusa	about 350 ft	46,500 acres
6	Whitefish Lake	about 233 ft	3,330 acres
7	Fort Peck Lake	about 220 ft	245,000 acres
8	Ashley Lake	about 220 ft	3,240 acres
9	Noxon Reservoir	about 200 ft	7,940 acres
10	Canyon Ferry Lake	about 166 ft	33,500 acres

1. Hungry Horse Reservoir

Hungry Horse Reservoir covers 23,600 acres of water. You will find it near Columbia Falls. Hungry Horse Dam holds it on the South Fork Flathead River. Trout are the draw. It goes down to about 500 ft. Hungry Horse Reservoir is impounded by Hungry Horse Dam on the South Fork of the Flathead River.

Hungry Horse Reservoir today: water temperature, bite times and the 3-D lake bed

2. Tally Lake

Tally Lake is a natural lake of some 1,330 acres. The lake is near Whitefish. Lake trout, trout and northern pike are the draw. The deepest water is around 492 ft. On the 3-D map the bed has three point drop-offs and two sheltered coves: good places to start. Tally Lake is the deepest lake entirely within Montana. It is a clear lake, so long casts and a quiet approach pay off.

Tally Lake today: water temperature, bite times and the 3-D lake bed

3. Lake McDonald

Lake McDonald covers 6,820 acres of water. It lies about 14 miles southwest of Columbia Falls. Like most lakes its size in Montana, it should hold largemouth bass, crappie, bluegill and catfish. The deepest water is around 472 ft. The lake bed gives you three point drop-offs and a sheltered cove to work. Lake McDonald is the largest lake in Glacier National Park and the deepest lake in the park.

Lake McDonald today: water temperature, bite times and the 3-D lake bed

4. Flathead Lake

At 126,000 acres of water, Flathead Lake is a huge piece of water. It holds lake trout, yellow perch, northern pike and trout. The deepest water is around 371 ft. On the 3-D map the bed has three point drop-offs and an upper arm: good places to start.

Flathead Lake today: water temperature, bite times and the 3-D lake bed

5. Lake Koocanusa

At 46,500 acres of water, Lake Koocanusa is a big lake. It lies near Eureka. Libby Dam holds it on the Kootenai River. Trout, kokanee salmon, largemouth bass and northern pike are the draw. At about 350 ft deep, it stays cooler below the surface well into summer. The lake bed gives you three point drop-offs and two sheltered coves to work. Lake Koocanusa is a transboundary reservoir that stretches from Montana north into British Columbia, Canada.

Lake Koocanusa today: water temperature, bite times and the 3-D lake bed

6. Whitefish Lake

At 3,330 acres, Whitefish Lake is a good-sized lake. The lake is next to Whitefish. It holds lake trout, trout, northern pike and yellow perch. At about 233 ft deep, it stays cooler below the surface well into summer. The lake bed gives you three point drop-offs and a sheltered cove to work. Whitefish Lake, next to the resort town of Whitefish, is an oligotrophic (clear, nutrient-poor) lake with lake trout that rival nearby Flathead Lake. It is a clear lake, so long casts and a quiet approach pay off.

Whitefish Lake today: water temperature, bite times and the 3-D lake bed

7. Fort Peck Lake

Fort Peck Lake covers 245,000 acres. It holds walleye, northern pike, lake trout and smallmouth bass. At about 220 ft deep, it stays cooler below the surface well into summer. The lake bed gives you three point drop-offs and a wind-blown bank to work.

Fort Peck Lake today: water temperature, bite times and the 3-D lake bed

8. Ashley Lake

At 3,240 acres of water, Ashley Lake is a good-sized lake. The lake is about 11 miles east of Kalispell. Expect trout, kokanee salmon and yellow perch. The deepest water is around 220 ft. The lake bed gives you three point drop-offs and a sheltered cove to work. Ashley Lake is one of the clearest lakes in Montana and is managed as a kokanee fishery. The water is known for being clear: lighter line and natural colours help.

Ashley Lake today: water temperature, bite times and the 3-D lake bed

9. Noxon Reservoir

Noxon Reservoir covers 7,940 acres of water. It lies about 70 miles west of Spokane Valley. Largemouth bass, smallmouth bass, northern pike and walleye are the draw. At about 200 ft deep, it stays cooler below the surface well into summer. Its bed shows three point drop-offs and two sheltered coves worth a first look. Noxon Reservoir on the Clark Fork River is a top smallmouth and largemouth bass fishery in Montana.

Noxon Reservoir today: water temperature, bite times and the 3-D lake bed

10. Canyon Ferry Lake

Canyon Ferry Lake spreads over 33,500 acres. The lake is within an easy drive of Great Falls (about 61 miles). Canyon Ferry Dam holds it on the Missouri River. It holds trout, walleye, northern pike and largemouth bass. At about 166 ft deep, it stays cooler below the surface well into summer. Its bed shows three steep ledges and an upper arm worth a first look. Canyon Ferry Lake, near Helena, is one of Montana's most popular fishing and boating destinations.

Canyon Ferry Lake today: water temperature, bite times and the 3-D lake bed

The clearest of them

Tally Lake, Whitefish Lake and Ashley Lake are known for clear water. On a clear lake fish see a long way: lighter line, natural colours and longer casts make the difference.

Fishing deep water

Deep lakes reward slow, vertical fishing: drop a jig or a spoon to the depth where fish show on the sonar and work it right there. In spring and fall the fish come shallow and any method works.