Minnesota · Cass County
Thunder Lake Fishing guide
Thunder Lake sits in Cass County, Minnesota, and covers 1,347 acres, reaching 95 ft at its deepest point. Average water clarity runs about 17.5 ft. The Minnesota DNR has surveyed the lake 21 times, most recently in 2025, with walleye, largemouth bass, smallmouth bass and northern pike in the nets.
DNR survey data
Fish species
WalleyeLast stocked 2025Fair numbers3.5per gill net14"Typical29"Biggest
Lengths measured · 74 fish
Recent · 2023Lengths measured · 3 fish
2025Only 3 fish measured that year — too few to read as a shape.
Lengths measured · 5 fish
2024Only 5 fish measured that year — too few to read as a shape.
Lengths measured · 12 fish
2023Lengths measured · 74 fish
2023Largemouth bassFair numbers38.8per hr (electrofishing)14"Typical18"Biggest
Lengths measured · 104 fish
Recent · 2023Lengths measured · 104 fish
2023Lengths measured · 154 fish
2017Lengths measured · 188 fish
2012Lengths measured · 192 fish
2006Smallmouth bassGood numbers27.5per hr (electrofishing)15"Typical19"Biggest
Lengths measured · 72 fish
Recent · 2023Lengths measured · 72 fish
2023Lengths measured · 71 fish
2017Lengths measured · 97 fish
2012Lengths measured · 71 fish
2006Northern pikeJust a few1.8per gill net27"Typical37"Biggest
Lengths measured · 21 fish
Recent · 2023Lengths measured · 21 fish
2023Lengths measured · 24 fish
2017Lengths measured · 16 fish
2012Lengths measured · 46 fish
2006BluegillJust a few12.5per trap net6"Typical8"Biggest
Lengths measured · 150 fish
Recent · 2023Lengths measured · 150 fish
2023Lengths measured · 498 fish
2017Lengths measured · 438 fish
2012Lengths measured · 762 fish
2006Yellow perchGood numbers5.9per gill net6"Typical11"Biggest
Lengths measured · 75 fish
Recent · 2023Lengths measured · 75 fish
2023Lengths measured · 386 fish
2017Lengths measured · 440 fish
2012Lengths measured · 410 fish
2006Rock bassOne of the best around5.3per trap net6"Typical11"Biggest
Lengths measured · 80 fish
Recent · 2023Lengths measured · 80 fish
2023Lengths measured · 158 fish
2017Lengths measured · 125 fish
2012Lengths measured · 232 fish
2006Rates come from standard DNR survey gear (gill nets, trap nets, electrofishing), judged against statewide benchmarks for the same gear, so the same number of fish per net can read differently for two species. Where the standard gear can't count a species reliably, only presence and size are listed. Typical is the middle fish of those measured. Open a row for the full length spread, survey by survey.
How to fish Thunder Lake through the year
Smallmouth bass
- Spring
- Smallmouth are on shallow rock, gravel and sand where they spawn. At 17.5 ft of clarity, fish them deeper and lighter than usual.
- Early summer
- Smallmouth are post-spawn on rock points, gravel bars and the adjacent breaks.
- Summer
- Smallmouth are on rock humps, points and hard-bottom breaks. On a lake that drops to 95 ft, check the deep edge of that structure too.
- Fall
- Smallmouth are bunched tight on deep rock, so find one and you have found the school.
Walleye
- Spring
- Walleye are shallow, on and just off the spawning flats and the first green weeds. At 17.5 ft of clarity, fish them deeper and lighter than usual.
- Early summer
- Walleye are setting up on the outside weed edge, points and shallow structure.
- Summer
- Walleye are working the weed edge, points and any wind-blown structure. On a lake that drops to 95 ft, check the deep edge of that structure too.
- Fall
- Walleye are packing onto the sharpest breaks and points as the water cools, in big schools with short windows.
Season patterns for each species. Open the live map for today's wind, light and water temp.
Size history
Biggest fish by survey year
| Survey year | Smallmouth bass | Walleye | Largemouth bass |
|---|---|---|---|
| 2025 | — | 6" | — |
| 2024 | — | 16" | — |
| 2023 | 19" | 28" | 18" |
| 2022 | — | 29" | — |
| 2021 | — | 23" | — |
| 2020 | — | 25" | — |
| 2019 | — | 16" | — |
| 2018 | — | 10" | — |
Longest fish measured by DNR survey crews in each year's nets. Survey gear samples the population, so the lake usually holds larger fish than any survey measured.
Suggested tackle
What to bring
Top presentations for this lake's structure and clarity:
Smallmouth bass · Soft plastics
Ned Rig
2.75" finesse stickbait or craw-style Ned bait
Walleye · Live bait
Live-Bait (Lindy) Rig + Leech/Crawler
jumbo leech or half a nightcrawler
Walleye · Trolling
Leadcore Line + Crankbaits
4–5" mid-diving crankbait behind a long leadcore run
Largemouth bass · Soft plastics
Texas-Rigged Worm
7" ribbon-tail or straight-tail plastic worm
Largemouth bass · Soft plastics
Free Rig
Creature bait or magnum finesse worm
Full setups, including hooks, weights and line, are on the live map. As an Amazon Associate I earn from qualifying purchases.
DNR stocking records
Stocking history
| Year | Species | Stocked |
|---|---|---|
| 2025 | Walleye | 11,752 fingerlings |
| 2023 | Walleye | 9,800 fingerlings |
| 2021 | Walleye | 9,040 fingerlings |
| 2019 | Walleye | 9,488 fingerlings |
| 2017 | Walleye | 7,534 fingerlings |
MN DNR · in their words
From the 2025 survey
Walleye fingerlings are currently stocked into Thunder Lake in odd numbered years at the rate of two pounds per littoral acre (452 pounds). Night electrofishing was conducted on Thunder Lake on September 10th, 2025, to monitor the abundance of young-of-the-year (YOY) Walleyes and evaluate the contribution of natural reproduction to the Walleye population. The total sample time was 2 hours, which resulted in a YOY Walleye catch rate of 1.5 per hour. Previous catch rates ranged from 0 to 228.3 per hour. Fish ranged in size from 6.1 to 6.7 inches, with a mean length of 6.5 inches. No age 1 and older Walleye were captured.
Narrative text from the Minnesota DNR lake survey.
Recent reports
Thunder Lake fishing reports
Recent reports on Thunder Lake from guides, tournaments and regular anglers. Anything posted in the last two weeks also bumps the matching spots on the live map, so you'll see a "matches a recent report" tag on them.
Public water access
Getting on the water
- Big Thunder Lake (trailer launch)
DNR bathymetry
Thunder Lake depth map
Within 30 miles
Nearby lakes
- Little Bass Lake · 136 ac · 1.9 mi
- Bass Lake · 195 ac · 3.2 mi
- Upper Trelipe Lake · 421 ac · 3.5 mi
- Island Lake · 358 ac · 3.7 mi
- Mitten Lake · 113 ac · 4.5 mi
- Little Thunder Lake · 258 ac · 5.1 mi
- Lower Trelipe Lake · 618 ac · 5.2 mi
- George Lake · 613 ac · 5.5 mi
Quick answers
Frequently asked questions
How deep is Thunder Lake?
Thunder Lake reaches 95 ft at its deepest point with a mean depth of 37 ft; about 17% of the lake is littoral (15 ft or shallower).
How big is Thunder Lake?
Thunder Lake covers 1,347 acres with about 15.9 miles of shoreline.
How clear is the water in Thunder Lake?
DNR Secchi readings on Thunder Lake average 17.5 ft of visibility, clear water for a Minnesota lake.
What fish are in Thunder Lake?
Minnesota DNR surveys (most recently 2025) record walleye, largemouth bass, smallmouth bass, northern pike, bluegill, crappie, yellow perch, rock bass.
Is Thunder Lake stocked?
Yes. The DNR stocked walleye in 2025; the stocking table on this page lists every year back to 2017.
Does Thunder Lake have a public access?
Yes. Thunder Lake has one public access site: Big Thunder Lake (trailer launch).
How big do smallmouth bass get in Thunder Lake?
The biggest smallmouth bass measured in recent DNR surveys taped 19"; the size-history table on this page tracks the biggest fish in each survey back to 2018.
When was Thunder Lake last surveyed?
The Minnesota DNR last surveyed Thunder Lake in 2025, the most recent of 21 surveys on record.
Page updated .
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