Grass Lake
Grass Lake in Shawano County, Wisconsin has a water quality grade of B (Good). Water clarity: 8.5 ft visibility. Phosphorus: 15.6 µg/L. Maximum depth: 52 ft. Surface area: 90 acres.
- Clarity
- 8.5 ft
- Typical in July
- 80°F
- Max depth
- 52 ft
- Area
- 90 acres
- Type
- Mesotrophic
- Trend
- → Stable
- Public access
- Yes
Next lake in Shawano County
Grass Lake is a 90-acre mesotrophic lake in Shawano County, Wisconsin with a maximum depth of 52 feet. Water quality is graded B based on 1 sampling years through 2026. Water clarity is declining over recent sampling years. The lake supports 6 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available. Compared to the 20 other monitored lakes in Shawano County, Grass Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-22. Grade methodology: LakeGrade methodology.
Watch Grass Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Grade onlyLow algae
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.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Moderate clarity, visible to about 8.5 ft. Phosphorus level: 15.6 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.5 ft | Not graded |
| Phosphorus | 15.6 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Grass Lake
Compare lakeside cabins, hotels, and vacation rentals near Grass Lake in Shawano County, Wisconsin — 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 Grass Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Water Temperature
Grass Lake typically sits around 80°F at the surface in July. Summer average is about 80°F. Usually warmest in Jul (about 80°F) and coldest in Apr (about 54°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 11 field readings (2024–2026) via the EPA Water Quality Portal. See the full Grass Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 52 ft |
| Surface Area | 90 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Grass Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1987. 3 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Water Quality Trend: → Stable
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.429 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.29 µg/L/yr | 7 |
EPA Impairment Status
Grass 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 WI10000097 · Official waterbody report · Matched by proximity (2.4 km)
County Ranking
Ranked #9 of 21 lakes in Shawano County
Nearby Lakes in Shawano County
Frequently asked questions about Grass Lake
What is the water quality grade for Grass Lake?
- Grass Lake in Shawano County, Wisconsin has a water quality grade of B (Good). Water clarity: 8.5 ft visibility. Phosphorus: 15.6 µg/L. Maximum depth: 52 ft. Surface area: 90 acres.
Is Grass Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Grass Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Grass Lake?
- Grass Lake typically sits around 80°F at the surface in July, from 11 EPA Water Quality Portal field readings (2024–2026). That is a typical value for the month, not a live reading.
How deep is Grass Lake?
- Grass Lake has a maximum depth of 52 feet. The lake covers 90 acres.
What fish are in Grass Lake?
- Fish species found in Grass Lake include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Grass Lake is located in Shawano County, Wisconsin.
Explore Grass Lake across LakeGrade
Fish species and top-graded lakes across Wisconsin
Fish species and best lakes in Shawano County
Species activity outlook by water temperature and season
Where to stay at Wisconsin's top lakes, each with its grade
Lakes in the Wolf River Watershed, ranked by water quality
Moderate nutrients, good water quality
Wisconsin's cleanest and most-polluted lakes, ranked
More Wisconsin Lake Rankings
Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
62 measurements from 1 monitoring station, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX62 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
- Total Phosphorus After Block Digestion
- 2130 B ~ Nephelometric Method
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)
Fish and recreation data from Wisconsin DNR Lakes