Willmert Lake
Willmert Lake in Martin County, Minnesota has a water quality grade of F (Algae-prone). 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.
- Clarity
- 3.3 ft
- Typical in August
- 73°F
- Max depth
- 8 ft
- Area
- 335 acres
- Type
- Eutrophic
- Public access
- Yes
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Willmert Lake →
Next lake in Martin County
Willmert Lake is a 335-acre productive, nutrient-rich eutrophic lake in Martin County, Minnesota with a maximum depth of 8 feet. Water quality is graded F based on 2 sampling years through 2025. The lake supports 11 documented fish species including bigmouth buffalo, black bullhead, and black crappie. Public access is available with 1 public boat landing. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
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)
Very murky, less than 3.3 ft of visibility. Phosphorus level: 68.5 µg/L. Chlorophyll-a: 52.1 µg/L. Trophic State Index: 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.3 ft | Not graded |
| Phosphorus | 68.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 52.1 µg/L | Poor |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay 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 grade measures nutrients and algae, not lodging — cabins and rentals around Willmert Lake are listed below.
Top-rated places to stay near Willmert Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Willmert Lake typically sits around 73°F at the surface in August. 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.
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
| Characteristic | Value |
|---|---|
| Maximum Depth | 8 ft |
| Surface Area | 335 acres |
| Shoreline Length | 3.3 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Wilmert LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Willmert Lake
County Ranking
Ranked #10 of 12 lakes in Martin County
Nearby Lakes in Martin County
Frequently asked questions about Willmert Lake
What is the water quality grade for Willmert Lake?
- Willmert Lake in Martin County, Minnesota has a water quality grade of F (Algae-prone). 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?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Willmert Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 52.1 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Willmert Lake?
- Willmert Lake typically sits around 73°F at the surface in August, 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.
Are there boat ramps on Willmert Lake?
- Willmert Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Wilmert Lake. Public access is listed as yes.
Explore Willmert Lake across LakeGrade
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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)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory