Thompson Lake
St. Louis County, Minnesota207 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Thompson Lake. Here is what has been measured.
- 9 ft max depth
- Limited data
Thompson Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Maximum depth: 9 ft. Surface area: 207.17 acres.
Minnesota DNR's Standard Survey on September 11, 2000 caught 5.00 northern pike per gill net at Thompson Lake. Length samples in the latest survey that recorded them ran 13–34 inches. DNR survey details →
Thompson Lake is a 207-acre lake in St. Louis County, Minnesota with a maximum depth of 9 feet. The lake supports 8 documented fish species including black bullhead, black crappie, and bluegill. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-10-17. Methodology: how these readings are compared.
What Thompson Lake is good for
From access and monitoring records, not editorial picks.
- Fishing8 species recorded
- Ice seasonIce-out around Apr 23
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Thompson Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Thompson Lake
These are the measurements Minnesota PCA publishes for Thompson Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 3 ft of visibility. TSI 61.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 61 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Thompson Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on September 11, 2000 caught 5.00 northern pike per gill net at Thompson Lake. Length samples in the latest survey that recorded them ran 13–34 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Thompson Lake’s water-quality measurements separately, and the water-quality trend over 4 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
2 surveys on file from MN DNR Fisheries. Most recent: 2000-09-11 (Standard Survey).
2 surveys on file · most recent 2000-09-11 (Standard Survey)
26 years old| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Black Bullhead | 68.88 | 4–7 in 2000-09-11 | 0.21 lb |
| Pumpkinseed | 4.76 | 3–6 in 2000-09-11 | 0.19 lb |
| White Sucker | 3.59 | 12–20 in 2000-09-11 | 3.41 lb |
| Northern Pike | 2.17 | 13–34 in 2000-09-11 | 2.21 lb |
| Yellow Perch | 1.86 | 2–7 in 2000-09-11 | 0.16 lb |
| Black Crappie | 1.64 | 4–11 in 2000-09-11 | 0.29 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Black Bullhead
Pumpkinseed
White Sucker
Northern Pike
From the 2000-09-11 survey
Results from the 2000 lake survey indicate that Thompson Lake is currently comprised of northern pike, yellow perch, black crappie, pumpkinseed sunfish, and black bullhead. There is no established boat access but walk-in access can be gained through county tax forfeit land on the south side of the lake. Thompson Lake…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Thompson Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — ThompsonFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Thompson (0486)Aquatic Plant Report · MN DNR LakeFinder
Lake Details
Max depth
9 ft
Surface area
207 acres
Shoreline
3.9 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
6 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,411 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Thompson Lake
Compare lakeside cabins, hotels, and vacation rentals near Thompson Lake in St. Louis County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Thompson Lake
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Follow Thompson Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Thompson Lake
Water Quality Trend: Stable
Based on 4 years of monitoring (2020–2023).
Water clarity
Stable4 years
Ice season
Typical ice-out
Apr 23
Earliest Apr 12, 2017 · Latest May 7, 2022
Typical ice-in
Nov 18
Earliest Nov 8, 2003 · Latest Dec 1, 2006
Most recent ice-out
May 3
2023
23 observations · Minnesota PCA ice records
Nearby Lakes in St. Louis County
Frequently asked questions about Thompson Lake
Where is Thompson Lake?
- Thompson Lake is a lake in St. Louis County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Thompson Lake?
- Thompson Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Maximum depth: 9 ft. Surface area: 207.17 acres.
Is Thompson Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Thompson Lake?
- Thompson Lake has a maximum depth of 9 feet. The lake covers 207.17 acres.
What fish are in Thompson Lake?
- Fish species found in Thompson Lake include black bullhead, black crappie, bluegill, largemouth bass, northern pike, pumpkinseed, white sucker, yellow perch. Thompson Lake is located in St. Louis County, Minnesota.
What did the DNR fisheries survey find at Thompson Lake?
- Minnesota DNR's Standard Survey on September 11, 2000 caught 5.00 northern pike per gill net at Thompson Lake. Length samples in the latest survey that recorded them ran 13–34 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Thompson Lake’s water-quality measurements separately, and the water-quality trend over 4 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
When does Thompson Lake thaw?
- Thompson Lake typically has ice-out around Apr 23. Ice typically forms around Nov 18. The open water season is approximately 209 days.
Can I fish at Thompson Lake?
- Public access to Thompson Lake is listed as no on the lake record, so confirm before you make the trip. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Thompson Lake across LakeQuality
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Where this data comes from
63 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA63 samples · 2020–2023
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate