Hay Lake
Hay Lake in Washington County, Minnesota has a water quality grade of C (Fair). Water clarity: 3.5 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.8 µg/L.
- Clarity
- 3.5 ft
- Typical in August
- 77°F
- Type
- Eutrophic
- Public access
- No
Next lake in Washington County
Hay Lake is a productive, nutrient-rich eutrophic lake in Washington County, Minnesota. Water quality is graded C based on 2 sampling years through 2024. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 74 other monitored lakes in Washington County, Hay Lake ranks #35 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-14. 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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Murky, only visible to about 3.5 ft. Phosphorus level: 30 µg/L. Chlorophyll-a: 4.8 µg/L. Trophic State Index: 53.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.5 ft | Not graded |
| Phosphorus | 30 µg/L | Fair |
| Chlorophyll-a (Algae) | 4.8 µg/L | Good |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Hay Lake
Compare lakeside cabins, hotels, and vacation rentals near Hay 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.
Top-rated places to stay near Hay Lake
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Water Temperature
Hay Lake typically sits around 77°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 78°F) and coldest in Apr (about 49°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 86 field readings (2010–2024) via the EPA Water Quality Portal. See the full Hay Lake water temperature breakdown →
Fishing Hay Lake
EPA Impairment Status
Hay 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 MN82-0068-00 · Official waterbody report · Matched by proximity (0.86 km)
County Ranking
Ranked #35 of 75 lakes in Washington County
Nearby Lakes With Higher Grades
Hay Lake holds Grade C. 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 Hay Lake
What is the water quality grade for Hay Lake?
- Hay Lake in Washington County, Minnesota has a water quality grade of C (Fair). Water clarity: 3.5 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.8 µg/L.
Is Hay Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Hay Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 4.8 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Hay Lake?
- Hay Lake typically sits around 77°F at the surface in August, from 86 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
Explore Hay Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Washington County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the St. Croix Watershed, ranked by water quality
High nutrients, frequent algae, reduced clarity
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near Hay Lake
Other Grade C Lakes in Minnesota
Eutrophic Lakes in Minnesota
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