Willmert Lake
Martin County, Minnesota335 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Willmert Lake. Here is what has been measured.
- Eutrophic
- 8 ft max depth
- Public access
- Limited data
Willmert Lake in Martin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 68.5 µg/L. Chlorophyll-a (algae): 52.1 µg/L. Maximum depth: 8 ft. Surface area: 335.44 acres.
Willmert Lake is a 335-acre productive, nutrient-rich eutrophic lake in Martin County, Minnesota with a maximum depth of 8 feet. The lake supports 11 documented fish species including bigmouth buffalo, black bullhead, and black crappie. Public access is available. Compared to the 11 other monitored lakes in Martin County, Willmert Lake ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-30. Methodology: how these readings are compared.
What Willmert Lake is good for
From access and monitoring records, not editorial picks.
- Fishing11 species recorded
Swimming conditions
Readings onlyLimited data
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 Willmert 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 Willmert Lake
These are the measurements Minnesota PCA publishes for Willmert 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 3.3 ft of visibility. Phosphorus 68.5 µg/L. Chlorophyll-a 52.1 µg/L. TSI 65.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 68.5µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 52.1µg/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. | 65 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Willmert Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Willmert Lake typically sits around 48°F at the surface in October. Summer average is about 76°F. Usually warmest in Jul (about 80°F) and coldest in Oct (about 48°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (48°F) to its warmest (80°F).
Typical surface water temperature by month, from 47 field readings (2017–2025) via the EPA Water Quality Portal. See the full Willmert Lake water temperature breakdown →
Lake Details
Max depth
8 ft
Surface area
335 acres
Shoreline
3.3 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
24 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,191 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Willmert Lake
Compare lakeside cabins, hotels, and vacation rentals near Willmert Lake in Martin 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 Willmert Lake are listed below.
Top-rated places to stay near Willmert 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 →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Willmert Lake
Nearby Lakes in Martin County
Frequently asked questions about Willmert Lake
Where is Willmert Lake?
- Willmert Lake is a lake in Martin County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Willmert Lake?
- Willmert Lake in Martin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 68.5 µg/L. Chlorophyll-a (algae): 52.1 µg/L. Maximum depth: 8 ft. Surface area: 335.44 acres.
Is Willmert Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Willmert Lake?
- Willmert Lake typically sits around 48°F at the surface in October, from 47 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Willmert Lake?
- Willmert Lake has a maximum depth of 8 feet. The lake covers 335.44 acres.
What fish are in Willmert Lake?
- Fish species found in Willmert Lake include bigmouth buffalo, black bullhead, black crappie, common carp, freshwater drum, largemouth bass, orangespotted sunfish, walleye, white crappie, white sucker, yellow perch. Willmert Lake is located in Martin County, Minnesota.
Can I fish at Willmert Lake?
- Public access to Willmert Lake is listed as yes on the lake record. 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 Willmert Lake across LakeQuality
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Species activity outlook by water temperature and season
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Where this data comes from
24 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA24 samples · 2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H 3 ~ Chlorophyll a-b-c Determination by fluorometer
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