Where is Forest Lake?

Forest Lake is a lake in Fond du Lac County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.

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.

Can I fish at Forest Lake?

Public access to Forest Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.

Forest Lake

Fond du Lac County, Wisconsin51 acresView map Directions

Wisconsin DNR publishes the water-quality measurements for Forest Lake. Here is what has been measured.

Clarity

14 ft

Clearer than most

Secchi · sampled 2026

Phosphorus

14.1 µg/L

Typical for Wisconsin

Measured by Wisconsin DNR

Water temp

~75°F

Typical for Aug · EPA WQP

Max depth

32 ft

Bathymetric survey

Area

51 acres

Surface area

Type

Mesotrophic

Trophic class

Mesotrophic
32 ft max depth
Public access

See the measurements Directions Where to stay

Forest Lake in Fond du Lac County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 14 ft visibility. Phosphorus: 14.1 µg/L. Maximum depth: 32 ft. Surface area: 51 acres.

Wisconsin DNR rates Panfish as abundant on Forest Lake. DNR survey details →

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Forest Lake is a 51-acre mesotrophic lake in Fond du Lac County, Wisconsin with a maximum depth of 32 feet. 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. 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. Methodology: how these readings are compared.

What Forest Lake is good for

From access and monitoring records, not editorial picks.

Clear water14 ft of visibility
Fishing4 species recorded
Deep water32 ft surveyed max depth

Swimming conditions

Readings only

Low algae

Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.

Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.

Whether Forest Lake is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

Compare swimming lakes near Oshkosh →

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Water quality measurements for Forest Lake

These are the measurements Wisconsin DNR publishes for Forest Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

Good clarity, visible to about 14 ft. Phosphorus 14.1 µg/L. TSI 41.

Water quality readings
Measure	Reading	Where it sits
Water clarity (Secchi depth)	14ft	Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer.
Total phosphorus	14.1µg/L	Good GoodFairPoor
Chlorophyll-a (algae)		No reading The green pigment in algae — a direct measure of how much algae is in the water.
Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a.	41	Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic

Moderate nutrients, good water quality

Ask about Forest Lake

Answers come straight from the public measurements and survey records on this page.

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.

Jan

Feb

45°

Mar

Apr

May

76°

Jun

79°

Jul

75°

Aug

Sep

Oct

Nov

Dec

Column height runs from this lake’s coldest month (45°F) to its warmest (79°F).

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 →

DNR fisheries survey

Wisconsin DNR rates Panfish as abundant on Forest Lake.

A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Forest Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.

WI DNR Lake Profile

Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1986. 3 stations on file (most recent sample 2025).

DNR Assessment

Excellent · Deep Seepage lake

Trophic State Index 40 (oligotrophic) · 5-year average

Fish Species (DNR-rated)

Panfish(Abundant)Largemouth Bass(Common)Northern Pike(Present)Walleye(Present)

Contour map (PDF) →Full WI DNR LakePage →Water quality stations →

Lake Details

Max depth

32 ft

Surface area

51 acres

Public access

Yes

Listed by Wisconsin DNR

Lake Size & Watershed

Watershed (drainage) area

7 sq mi

HydroLAKES / HydroSHEDS

Shoreline

1.2 mi

HydroLAKES / HydroSHEDS

Elevation

997 ft

Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).

Stays via Stay22

Stays 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

Prices for Oct 9–11, 4 adults. Change dates on the map below.

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 →

Follow Forest Lake’s readings

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Fish Species

Panfish Largemouth Bass Northern Pike Walleye

Click a species to see every 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.

Eurasian Water-MilfoilHybrid Eurasian / Northern Water-Milfoil

Water Quality Trend: Improving

Based on 7 years of monitoring (2020–2026).

Water clarity
Improving
6 years
Phosphorus
Improving
-4.28 µg/L/yr7 years

See year-by-year chart →

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, Inc
Adell · 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.

Nearby Lakes in Fond du Lac County

Mauthe Lake6 ft clear · Eutrophic—View →Auburn Lake7.6 ft clear · Mesotrophic—View →Birchwood Lake—View →Kettle Moraine Lake11 ft clear · Mesotrophic—View →Long Lake9.1 ft clear · Mesotrophic—View →Dickman Lake—View →

Frequently asked questions about Forest Lake

Where is Forest Lake?: Forest Lake is a lake in Fond du Lac County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Forest Lake?: Forest Lake in Fond du Lac County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. 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?: Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
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.
What did the DNR fisheries survey find at Forest Lake?: Wisconsin DNR rates Panfish as abundant on Forest Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Forest Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Forest Lake?: Public access to Forest Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.

Explore Forest Lake across LakeQuality

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Official ratings and named-lake measurements

State Parks Near Forest Lake

Harrington Beach State Park

State Park · 20 mi

Kohler-Andrae State Park

State Park · 22.6 mi

Other Lakes in Wisconsin

Lake Ellen

Sheboygan County · 9 ft

Green Lake

Washington County · 9 ft

Random Lake

Sheboygan County · 4.5 ft

Little Cedar Lake

Washington County · 10.5 ft

Sandhill Lake

Ozaukee County · 7.5 ft

Crystal Lake

Sheboygan County · 20 ft

Mesotrophic Lakes in Wisconsin

Lake Ellen Green Lake Big Cedar Lake-North Site-Near West Bend Little Cedar Lake

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 ResourcesWIDNR_WQX56 samples · 2021–2026

Analytical methods

Phosphorus by Colorimetry

Monitoring station identifiers (1)

WIDNR_WQX-203076

EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.

Other records on this page

Regulated discharger data from EPA ECHO (ICIS-NPDES)

Lake size & watershed from HydroLAKES (HydroSHEDS)

Fish and recreation data from Wisconsin DNR Lakes