Long Lake
Long Lake in Sauk County, Wisconsin has a water quality grade of C (Fair). Water clarity: 4.1 ft visibility. Phosphorus: 27.9 µg/L.
- Clarity
- 4.1 ft
- Typical in August
- 71°F
- Type
- Eutrophic
- Trend
- → Stable
- Public access
- Yes
Next lake in Sauk County
Long Lake is a productive, nutrient-rich eutrophic lake in Sauk County, Wisconsin. Water quality is graded C based on 1 sampling years through 2026. Water clarity is declining over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 6 other monitored lakes in Sauk County, Long Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-05-27. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyModerate
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Murky, only visible to about 4.1 ft. Phosphorus level: 27.9 µg/L. Trophic State Index: 54.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.1 ft | Not graded |
| Phosphorus | 27.9 µg/L | Fair |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 54 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long Lake in Sauk 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 Long Lake
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Water Temperature
Long Lake typically sits around 71°F at the surface in August. Summer average is about 75°F. Usually warmest in Jun (about 79°F) and coldest in Oct (about 50°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 34 field readings (2024–2025) via the EPA Water Quality Portal. See the full Long Lake water temperature breakdown →
Recreation & Access
- McKenna RoadPublic
- Otter CreekPublic
Fishing Long Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.263 m/yr | 5 |
| Phosphorus | ↑ Improving | -3.24 µg/L/yr | 5 |
County Ranking
Ranked #3 of 7 lakes in Sauk County
Nearby Lakes With Higher Grades
Long Lake holds Grade C. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Sauk County
Frequently asked questions about Long Lake
What is the water quality grade for Long Lake?
- Long Lake in Sauk County, Wisconsin has a water quality grade of C (Fair). Water clarity: 4.1 ft visibility. Phosphorus: 27.9 µg/L.
Is Long Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Long Lake has a water quality grade of C (Fair). Always check local health department advisories before swimming.
What is the water temperature of Long Lake?
- Long Lake typically sits around 71°F at the surface in August, from 34 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
Are there boat ramps on Long Lake?
- Long Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include McKenna Road, Otter Creek. Public access is listed as yes.
Explore Long Lake across LakeGrade
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Species activity outlook by water temperature and season
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High nutrients, frequent algae, reduced clarity
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State Parks Near Long Lake
Other Grade C Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Where this data comes from
84 measurements from 2 monitoring stations, 2021–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX84 samples · 2021–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (2)
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
Named boat-access points from the USGS National Boat Ramps inventory