Oak Lake
Polk County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Oak Lake. Here is what has been measured.
- Eutrophic
- 33 ft max depth
Oak Lake in Polk County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 113 µg/L. Chlorophyll-a (algae): 30.7 µg/L.
Oak Lake is a productive, nutrient-rich eutrophic lake in Polk County, Minnesota with an estimated average depth of about 33 feet. 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 18 other monitored lakes in Polk County, Oak Lake ranks #17 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-23. Methodology: how these readings are compared.
What Oak Lake is good for
From access and monitoring records, not editorial picks.
- Ice seasonIce-out around Apr 12
Swimming conditions
Readings onlyAlgae risk
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Oak 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 Oak Lake
These are the measurements Minnesota PCA publishes for Oak 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. Phosphorus 113 µg/L. Chlorophyll-a 30.7 µg/L. TSI 66.
| 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 | 113µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 30.7µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 66 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Oak 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 Oak Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (469,894 cells/mL) on July 19, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
Max depth
~33 ft est.
Public access
No
Listed by Minnesota PCA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Oak Lake.
Lake Size & Watershed
Watershed (drainage) area
12 sq mi
HydroLAKES / HydroSHEDS
Surface area
348 acres
HydroLAKES / HydroSHEDS
Shoreline
2.9 mi
HydroLAKES / HydroSHEDS
Elevation
1,188 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Stays via Stay22
Stays near Oak Lake
Compare lakeside cabins, hotels, and vacation rentals near Oak Lake in Polk 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Oak Lake are listed below.
Top-rated places to stay near Oak Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fishing Oak Lake
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Improving-32.71 µg/L/yr6 years
Chlorophyll-a
Improving-11.77 µg/L/yr6 years
Ice season
Typical ice-out
Apr 12
Earliest Mar 20, 2012 · Latest May 8, 2013
Most recent ice-out
Apr 27
2020
11 observations · Minnesota PCA ice records
Nearby Lakes in Polk County
Frequently asked questions about Oak Lake
Where is Oak Lake?
- Oak Lake is a lake in Polk County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Oak Lake?
- Oak Lake in Polk County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 113 µg/L. Chlorophyll-a (algae): 30.7 µg/L.
Is Oak Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Oak Lake?
- No published bathymetric survey covers Oak Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 33 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
When does Oak Lake thaw?
- Oak Lake typically has ice-out around Apr 12.
Does Oak Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Oak Lake (clouds, ice, or an off-season gap). The most recent reading was high (469,894 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Can I fish at Oak Lake?
- Public access to Oak 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 Oak Lake across LakeQuality
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Where this data comes from
87 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA87 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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