Lake Poygan
Lake Poygan in Winnebago County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 2.5 ft visibility. Maximum depth: 11 ft. Surface area: 14024 acres.
Wisconsin DNR rates Panfish, Sturgeon, and Catfish as abundant on Lake Poygan. DNR survey details →
- Clarity
- 2.5 ft
- Typical in August
- 74°F
- Max depth
- 11 ft
- Area
- 14,024 acres
- Trend
- → Stable
- Public access
- Yes
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Why Lake Poygan has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Lake Poygan, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by WI DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Lake Poygan is a 14,024-acre lake in Winnebago County, Wisconsin with a maximum depth of 11 feet. The lake supports 8 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available with 3 public boat landings.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-05-27. Grade methodology: LakeQuality methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Lake Poygan
These readings exist but are not enough for an A–F grade — see why.
Very murky, less than 2.5 ft of visibility. Trophic State Index: 64.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Poygan
Compare lakeside cabins, hotels, and vacation rentals near Lake Poygan in Winnebago 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 Lake Poygan
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Planning a trip? Cabins and lodging at Lake Poygan → · more Wisconsin lake trips
Water Temperature
Lake Poygan typically sits around 74°F at the surface in August. Summer average is about 75°F. Usually warmest in Jul (about 76°F) and coldest in Oct (about 52°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 46 field readings (2024–2026) via the EPA Water Quality Portal. See the full Lake Poygan water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Lake Poygan — clouds, ice, or an off-season gap in coverage. The most recent reading was high (539,511 cells/mL) on July 18, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Wisconsin DNR rates Panfish, Sturgeon, and Catfish as abundant on Lake Poygan.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality does not assign an A–F grade on Lake Poygan — official chemistry is on file, not a letter, and the water-quality trend over 6 years of monitoring is stable. 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. 17 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 11 ft |
| Surface Area | 14,024 acres |
| Public Access | Yes |
Recreation & Access
- Boom BayPublic
- Poygan Shores LanePublic
- Lake PoyganPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Lake Poygan
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.026 m/yr | 6 |
EPA Impairment Status
Lake Poygan is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit WI10006159 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lake Poygan under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Poygan Poy Sippi Sd 1 WwtfWinneconne · 1.6 mi away · NPDES WI0035513Recent violation
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.
Graded lakes near Lake Poygan
Lake Poygan has no grade, but these lakes within a short drive do.
Nearby Lakes in Winnebago County
Frequently asked questions about Lake Poygan
Where is Lake Poygan?
- Lake Poygan is a lake in Winnebago County, Wisconsin. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Lake Poygan?
- Lake Poygan in Winnebago County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 2.5 ft visibility. Maximum depth: 11 ft. Surface area: 14024 acres.
Is Lake Poygan safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Lake Poygan is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of Lake Poygan?
- Lake Poygan typically sits around 74°F at the surface in August, from 46 EPA Water Quality Portal field readings (2024–2026). That is a typical value for the month, not a live reading.
How deep is Lake Poygan?
- Lake Poygan has a maximum depth of 11 feet. The lake covers 14024 acres.
What fish are in Lake Poygan?
- Fish species found in Lake Poygan include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye, Sturgeon, Catfish. Lake Poygan is located in Winnebago County, Wisconsin.
What did the DNR fisheries survey find at Lake Poygan?
- Wisconsin DNR rates Panfish, Sturgeon, and Catfish as abundant on Lake Poygan. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality does not assign an A–F grade on Lake Poygan — official chemistry is on file, not a letter, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
Does Lake Poygan have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Lake Poygan (clouds, ice, or an off-season gap). The most recent reading was high (539,511 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Are there boat ramps on Lake Poygan?
- Lake Poygan has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Boom Bay, Poygan Shores Lane, Lake Poygan. Public access is listed as yes.
Explore Lake Poygan across LakeQuality
Depth, room, public access, and the state wake-sport rules
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Species activity outlook by water temperature and season
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Where this data comes from
54 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_WQX54 samples · 2020–2026
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