Slate Lake
Slate Lake in Lake County, Minnesota has a water quality grade of A (Excellent). Water clarity: 4.4 ft visibility. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 4.6 µg/L. Maximum depth: 7 ft. Surface area: 293.02 acres.
- Clarity
- 4.4 ft
- Typical in August
- 72°F
- Max depth
- 7 ft
- Area
- 293 acres
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- May 1
Next lake in Lake County
Slate Lake is a 293-acre mesotrophic lake in Lake County, Minnesota with a maximum depth of 7 feet. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 8 documented fish species including bluegill, northern pike, and pumpkinseed. Public access is available with 1 public boat landing. Compared to the 34 other monitored lakes in Lake County, Slate Lake ranks #19 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-16. 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)
Murky, only visible to about 4.4 ft. Phosphorus level: 22 µg/L. Chlorophyll-a: 4.6 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.4 ft | Not graded |
| Phosphorus | 22 µg/L | Good |
| Chlorophyll-a (Algae) | 4.6 µg/L | Good |
| Trophic State Index (TSI) | 50 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Slate Lake
Compare lakeside cabins, hotels, and vacation rentals near Slate Lake in Lake 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
Slate Lake typically sits around 72°F at the surface in August. Summer average is about 71°F. Usually warmest in Jun (about 73°F) and coldest in May (about 50°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 15 field readings (2025–2025) via the EPA Water Quality Portal. See the full Slate Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 7 ft |
| Surface Area | 293 acres |
| Shoreline Length | 8.1 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- East Chub LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Slate Lake
Water Quality Trend: ↓ Declining
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -1.555 m/yr | 3 |
Ice Season
Historical ice data from Minnesota DNR (6 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2026-04-24 (2026) | 2023-05-05 (2023) |
| Ice-In | 2022-11-12 (2022) | 2024-11-26 (2024) |
Most recent ice-out: 2026-04-24
EPA Impairment Status
Slate 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 MN38-0666-00 · Official waterbody report
County Ranking
Ranked #19 of 35 lakes in Lake County
Nearby Lakes in Lake County
Frequently asked questions about Slate Lake
What is the water quality grade for Slate Lake?
- Slate Lake in Lake County, Minnesota has a water quality grade of A (Excellent). Water clarity: 4.4 ft visibility. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 4.6 µg/L. Maximum depth: 7 ft. Surface area: 293.02 acres.
Is Slate Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Slate Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 4.6 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Slate Lake?
- Slate Lake typically sits around 72°F at the surface in August, from 15 EPA Water Quality Portal field readings (2025–2025). That is a typical value for the month, not a live reading.
How deep is Slate Lake?
- Slate Lake has a maximum depth of 7 feet. The lake covers 293.02 acres.
What fish are in Slate Lake?
- Fish species found in Slate Lake include bluegill, northern pike, pumpkinseed, rock bass, smallmouth bass, walleye, white sucker, yellow perch. Slate Lake is located in Lake County, Minnesota.
When does Slate Lake thaw?
- Slate Lake typically has ice-out around May 1.
Are there boat ramps on Slate Lake?
- Slate Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include East Chub Lake. Public access is listed as yes.
Explore Slate Lake across LakeGrade
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Where this data comes from
15 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
MNPCA15 samples · 2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate