Mud Lake
Mud Lake in Washington County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.2 ft visibility. Phosphorus: 89 µg/L. Chlorophyll-a (algae): 87 µg/L.
- Clarity
- 1.2 ft
- Typical in August
- 67°F
- Type
- Hypereutrophic
- 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 Mud Lake →
Next lake in Washington County
Mud Lake is a highly nutrient-loaded hypereutrophic lake in Washington County, Minnesota. Water quality is graded F based on 2 sampling years through 2024. 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 74 other monitored lakes in Washington County, Mud Lake ranks #64 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-07. 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 1.2 ft of visibility. Phosphorus level: 89 µg/L. Chlorophyll-a: 87 µg/L. Trophic State Index: 72.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.2 ft | Not graded |
| Phosphorus | 89 µg/L | Poor |
| Chlorophyll-a (Algae) | 87 µg/L | Poor |
| Trophic State Index (TSI) | 72 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Mud Lake
Compare lakeside cabins, hotels, and vacation rentals near Mud Lake in Washington 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 Mud Lake are listed below.
Top-rated places to stay near Mud Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Mud Lake typically sits around 67°F at the surface in August. Summer average is about 70°F. Usually warmest in Jul (about 74°F) and coldest in Oct (about 51°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 18 field readings (2010–2024) via the EPA Water Quality Portal. See the full Mud Lake water temperature breakdown →
Fishing Mud Lake
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.094 m/yr | 6 |
| Phosphorus | ↑ Improving | -6.8 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +1.13 µg/L/yr | 6 |
EPA Impairment Status
Mud Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN62-0001-00 · Official waterbody report · Matched by proximity (1.73 km)
County Ranking
Ranked #64 of 75 lakes in Washington County
Nearby Lakes With Higher Grades
Mud Lake holds Grade F. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Washington County
Frequently asked questions about Mud Lake
What is the water quality grade for Mud Lake?
- Mud Lake in Washington County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.2 ft visibility. Phosphorus: 89 µg/L. Chlorophyll-a (algae): 87 µg/L.
Is Mud 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. Mud Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 87 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Mud Lake?
- Mud Lake typically sits around 67°F at the surface in August, from 18 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
Explore Mud Lake across LakeGrade
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Species activity outlook by water temperature and season
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Very high nutrients, dense algae, poor clarity
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State Parks Near Mud Lake
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Where this data comes from
28 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA28 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
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