Forest Lake
Forest Lake in Fond du Lac County, Wisconsin has a water quality grade of B (Good). Water clarity: 14 ft visibility. Phosphorus: 14.1 µg/L. Maximum depth: 32 ft. Surface area: 51 acres.
- Clarity
- 14 ft
- Typical in August
- 75°F
- Max depth
- 32 ft
- Area
- 51 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in Fond du Lac County
Forest Lake is a 51-acre mesotrophic lake in Fond du Lac County, Wisconsin with a maximum depth of 32 feet. Water quality is graded B based on 1 sampling years through 2026. Overall water quality is improving over recent sampling years. The lake supports 4 documented fish species including Panfish, Largemouth Bass, and Northern Pike. Public access is available with 3 public boat landings. Compared to the 8 other monitored lakes in Fond du Lac County, Forest Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-07. Grade methodology: LakeGrade methodology.
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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)
Good clarity, visible to about 14 ft. Phosphorus level: 14.1 µg/L. Trophic State Index: 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14 ft | Not graded |
| Phosphorus | 14.1 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Forest Lake
Compare lakeside cabins, hotels, and vacation rentals near Forest Lake in Fond du Lac 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 Forest Lake
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Water Temperature
Forest Lake typically sits around 75°F at the surface in August. Summer average is about 77°F. Usually warmest in Jul (about 79°F) and coldest in Mar (about 45°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 8 field readings (2024–2025) via the EPA Water Quality Portal. See the full Forest Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 32 ft |
| Surface Area | 51 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Beechwood LakePublic
- Crooked LakePublic
- Lake SevenPublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Forest 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 1986. 3 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.893 m/yr | 6 |
| Phosphorus | ↑ Improving | -4.28 µg/L/yr | 7 |
EPA Impairment Status
Forest 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 WI10001196 · Official waterbody report · Matched by proximity (1.37 km)
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Forest Lake under Clean Water Act (NPDES) discharge permits.
- Noble View Cheese Company, IncAdell · 2.5 mi away · NPDES WI0052981
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #3 of 9 lakes in Fond du Lac County
Nearby Lakes in Fond du Lac County
Frequently asked questions about Forest Lake
What is the water quality grade for Forest Lake?
- Forest Lake in Fond du Lac County, Wisconsin has a water quality grade of B (Good). Water clarity: 14 ft visibility. Phosphorus: 14.1 µg/L. Maximum depth: 32 ft. Surface area: 51 acres.
Is Forest Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Forest Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Forest Lake?
- Forest Lake typically sits around 75°F at the surface in August, from 8 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Forest Lake?
- Forest Lake has a maximum depth of 32 feet. The lake covers 51 acres.
What fish are in Forest Lake?
- Fish species found in Forest Lake include Panfish, Largemouth Bass, Northern Pike, Walleye. Forest Lake is located in Fond du Lac County, Wisconsin.
Are there boat ramps on Forest Lake?
- Forest Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Beechwood Lake, Crooked Lake, Lake Seven. Public access is listed as yes.
Explore Forest Lake across LakeGrade
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Moderate nutrients, good water quality
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Where this data comes from
56 measurements from 1 monitoring station, 2021–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX56 samples · 2021–2026
Analytical methods
- Phosphorus by Colorimetry
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory