Thomas Lake
Lake County, Minnesota1,465 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Thomas Lake. Here is what has been measured.
- Impaired · Mercury
- 110 ft max depth
- Limited data
Thomas Lake in Lake County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 14.2 ft visibility. Maximum depth: 110 ft. Surface area: 1465.19 acres.
Minnesota DNR's Standard Survey on September 10, 2012 caught 13.67 walleye per gill net at Thomas Lake. Length samples in the latest survey that recorded them ran 7–25 inches. DNR survey details →
Free interactive depth-contour map of Thomas Lake, reaching a maximum surveyed depth of 110 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Thomas Lake is a 1,465-acre lake in Lake County, Minnesota with a maximum depth of 110 feet. Limited fish-species data available. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-01. Methodology: how these readings are compared.
What Thomas Lake is good for
From access and monitoring records, not editorial picks.
- Clear water14.2 ft of visibility
- Deep water110 ft surveyed max depth
- Big water1,465 acres
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Thomas Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Thomas 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 Thomas Lake
These are the measurements Minnesota PCA publishes for Thomas Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 14.2 ft. TSI 39.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 14.2ft | 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. | 39 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Thomas Lake
Answers come straight from the public measurements and survey records on this page.
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Thomas Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (310,456 cells/mL) on November 29, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Standard Survey on September 10, 2012 caught 13.67 walleye per gill net at Thomas Lake. Length samples in the latest survey that recorded them ran 7–25 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Thomas Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
4 surveys on file from MN DNR Fisheries. Most recent: 2025-08-03 (Targeted Survey).
4 surveys on file · most recent 2025-08-03 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Walleye | 8.00 | 7–25 in 2012-09-10 | 2.25 lb |
| Tullibee (Cisco) | 7.19 | 6–10 in 2012-09-10 | 0.1 lb |
| White Sucker | 2.05 | 8–20 in 2012-09-10 | 1.92 lb |
| Lake Trout | 1.60 | 10–35 in 2012-09-10 | 3.24 lb |
| Rock Bass | 0.75 | 5–7 in 2012-09-10 | 0.16 lb |
| Northern Pike | 0.69 | 18–30 in 2012-09-10 | 4.23 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.
Walleye
Tullibee (Cisco)
White Sucker
Lake Trout
From the 2025-08-03 survey
Temperature and dissolved oxygen measurements were collected from the deepest basin in Thomas Lake on August 3rd, 2025. This was done to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Trout, the most sensitive coldwater species present in this lake (Cisco, also…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Thomas Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — ThomasFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
110 ft
Surface area
1,465 acres
Shoreline
26.2 mi
Littoral zone
30%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
182 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,526 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Thomas Lake
Compare lakeside cabins, hotels, and vacation rentals near Thomas Lake in Lake 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 Thomas Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Follow Thomas Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Thomas Lake
Water Quality Trend: Stable
Based on 5 years of monitoring (2020–2025).
Water clarity
Stable5 years
EPA Impairment Status
Thomas Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN38-0351-00 · Official waterbody report
Nearby Lakes in Lake County
Frequently asked questions about Thomas Lake
Where is Thomas Lake?
- Thomas Lake is a lake in Lake County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Thomas Lake?
- Thomas Lake in Lake County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 14.2 ft visibility. Maximum depth: 110 ft. Surface area: 1465.19 acres.
Is Thomas Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Thomas Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Thomas Lake?
- Thomas Lake has a maximum depth of 110 feet. The lake covers 1465.19 acres.
What did the DNR fisheries survey find at Thomas Lake?
- Minnesota DNR's Standard Survey on September 10, 2012 caught 13.67 walleye per gill net at Thomas Lake. Length samples in the latest survey that recorded them ran 7–25 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Thomas Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
Does Thomas Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Thomas Lake (clouds, ice, or an off-season gap). The most recent reading was high (310,456 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Can I fish at Thomas Lake?
- Public access to Thomas 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 Thomas Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Lake County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
Other Lakes in Minnesota
Oligotrophic Lakes in Minnesota
Where this data comes from
37 measurements from 20 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA37 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (20)
- MNPCA-38-0351-00-225
- MNPCA-38-0351-00-100
- MNPCA-38-0351-00-228
- MNPCA-38-0351-00-229
- MNPCA-38-0351-00-227
- MNPCA-38-0351-00-206
- MNPCA-38-0351-00-201
- MNPCA-38-0351-00-226
- MNPCA-38-0351-00-219
- MNPCA-38-0351-00-215
- MNPCA-38-0351-00-211
- MNPCA-38-0351-00-207
- MNPCA-38-0351-00-224
- MNPCA-38-0351-00-223
- MNPCA-38-0351-00-203
- MNPCA-38-0351-00-212
- MNPCA-38-0351-00-221
- MNPCA-38-0351-00-216
- MNPCA-38-0351-00-202
- MNPCA-38-0351-00-210
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder