Mays Lake
Mays Lake in Washington County, Minnesota has a water quality grade of A (Excellent). Water clarity: 11 ft visibility. Phosphorus: 16 µg/L. Chlorophyll-a (algae): 4.1 µg/L. Maximum depth: 25 ft. Surface area: 40.22 acres.
- Clarity
- 11 ft
- Typical in August
- 76°F
- Max depth
- 25 ft
- Area
- 40 acres
- Type
- Mesotrophic
- Trend
- → Stable
- Public access
- No
- Ice-out
- Mar 20
Next lake in Washington County
Mays Lake is a 40-acre mesotrophic lake in Washington County, Minnesota with a maximum depth of 25 feet. Water quality is graded A based on 2 sampling years through 2024. Phosphorus level is declining 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, Mays Lake ranks #20 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-17. 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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Good clarity, visible to about 11 ft. Phosphorus level: 16 µg/L. Chlorophyll-a: 4.1 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11 ft | Not graded |
| Phosphorus | 16 µg/L | Good |
| Chlorophyll-a (Algae) | 4.1 µg/L | Good |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Mays Lake
Compare lakeside cabins, hotels, and vacation rentals near Mays 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.
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Water Temperature
Mays Lake typically sits around 76°F at the surface in August. Summer average is about 73°F. Usually warmest in Aug (about 76°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 100 field readings (2011–2024) via the EPA Water Quality Portal. See the full Mays Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 25 ft |
| Surface Area | 40 acres |
| Shoreline Length | 1.8 mi |
| Littoral Zone | 57% |
| Public Access | No |
Fishing Mays Lake
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.048 m/yr | 6 |
| Phosphorus | ↓ Declining | +1.75 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -0.3 µg/L/yr | 2 |
Ice Season
Historical ice data from Minnesota DNR (4 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2012-03-19 (2012) | 2009-04-04 (2009) |
| Ice-In | 2012-11-23 (2012) | 2012-11-23 (2012) |
Most recent ice-out: 2012-03-19
EPA Impairment Status
Mays 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 MN82-0046-00 · Official waterbody report · Matched by proximity (1.77 km)
County Ranking
Ranked #20 of 75 lakes in Washington County
Nearby Lakes in Washington County
Frequently asked questions about Mays Lake
What is the water quality grade for Mays Lake?
- Mays Lake in Washington County, Minnesota has a water quality grade of A (Excellent). Water clarity: 11 ft visibility. Phosphorus: 16 µg/L. Chlorophyll-a (algae): 4.1 µg/L. Maximum depth: 25 ft. Surface area: 40.22 acres.
Is Mays Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Mays Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 4.1 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Mays Lake?
- Mays Lake typically sits around 76°F at the surface in August, from 100 EPA Water Quality Portal field readings (2011–2024). That is a typical value for the month, not a live reading.
How deep is Mays Lake?
- Mays Lake has a maximum depth of 25 feet. The lake covers 40.22 acres.
When does Mays Lake thaw?
- Mays Lake typically has ice-out around Mar 20.
Explore Mays Lake across LakeGrade
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Where this data comes from
48 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
MNPCA48 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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate