Thomas Lake
Thomas Lake in Hennepin County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 3.4 ft visibility. Phosphorus: 78.3 µg/L. Chlorophyll-a (algae): 34.1 µg/L.
- Clarity
- 3.4 ft
- Typical in August
- 59°F
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- No
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Thomas Lake →
Next lake in Hennepin County
Thomas Lake is a productive, nutrient-rich eutrophic lake in Hennepin County, Minnesota. Water quality is graded F based on 3 sampling years through 2022. Overall water quality is improving over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 80 other monitored lakes in Hennepin County, Thomas Lake ranks #68 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-09-20. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyAlgae risk
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Murky, only visible to about 3.4 ft. Phosphorus level: 78.3 µg/L. Chlorophyll-a: 34.1 µg/L. Trophic State Index: 64.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.4 ft | Not graded |
| Phosphorus | 78.3 µg/L | Poor |
| Chlorophyll-a (Algae) | 34.1 µg/L | Poor |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Thomas Lake
Compare lakeside cabins, hotels, and vacation rentals near Thomas Lake in Hennepin 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Thomas Lake are listed below.
Top-rated places to stay near Thomas Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Thomas Lake typically sits around 59°F at the surface in August. Summer average is about 57°F. Usually warmest in Aug (about 59°F) and coldest in Apr (about 40°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 109 field readings (2021–2022) via the EPA Water Quality Portal. See the full Thomas Lake water temperature breakdown →
Fishing Thomas Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.254 m/yr | 5 |
| Phosphorus | ↑ Improving | -36.64 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -20.31 µg/L/yr | 5 |
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN27-0149-00 · Official waterbody report · Matched by proximity (1.38 km)
County Ranking
Ranked #68 of 81 lakes in Hennepin County
Nearby Lakes With Higher Grades
Thomas Lake holds Grade F. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Hennepin County
Frequently asked questions about Thomas Lake
What is the water quality grade for Thomas Lake?
- Thomas Lake in Hennepin County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 3.4 ft visibility. Phosphorus: 78.3 µg/L. Chlorophyll-a (algae): 34.1 µg/L.
Is Thomas Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Thomas Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 34.1 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Thomas Lake?
- Thomas Lake typically sits around 59°F at the surface in August, from 109 EPA Water Quality Portal field readings (2021–2022). That is a typical value for the month, not a live reading.
Explore Thomas Lake across LakeGrade
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Where this data comes from
52 measurements from 1 monitoring station, 2021–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA52 samples · 2021–2022
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 4500 N C ~ Persufate Method for Total Nitrogen
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database