Long Lake
Long Lake in Bayfield County, Wisconsin has a water quality grade of B (Good). Water clarity: 16.2 ft visibility. Phosphorus: 13.8 µg/L. Maximum depth: 28 ft. Surface area: 280 acres.
- Clarity
- 16.2 ft
- Typical in August
- 74°F
- Max depth
- 28 ft
- Area
- 280 acres
- Type
- Oligotrophic
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in Bayfield County
Long Lake is a 280-acre cold, clear oligotrophic lake in Bayfield County, Wisconsin with a maximum depth of 28 feet. Water quality is graded B based on 1 sampling years through 2025. 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 2 public boat landings. Compared to the 23 other monitored lakes in Bayfield County, Long Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-08-21. 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)
Crystal clear, you can see 16.2 ft down. Phosphorus level: 13.8 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.2 ft | Not graded |
| Phosphorus | 13.8 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long Lake in Bayfield 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.
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Water Temperature
Long Lake typically sits around 74°F at the surface in August. Summer average is about 73°F. Usually warmest in Jul (about 74°F) and coldest in May (about 66°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 11 field readings (2024–2025) via the EPA Water Quality Portal. See the full Long Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Long Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (285,759 cells/mL) on April 7, 2024.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 28 ft |
| Surface Area | 280 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Jackman LakePublic
- Long LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Long 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 1995. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Long Lake covering fish populations, stocking, water quality, and management. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2024Long Lake spring shocking survey, 2024Spring Shocking Survey · WI DNR · 2024 (PDF)
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.05 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.55 µg/L/yr | 6 |
County Ranking
Ranked #2 of 24 lakes in Bayfield County
Nearby Lakes in Bayfield County
Frequently asked questions about Long Lake
What is the water quality grade for Long Lake?
- Long Lake in Bayfield County, Wisconsin has a water quality grade of B (Good). Water clarity: 16.2 ft visibility. Phosphorus: 13.8 µg/L. Maximum depth: 28 ft. Surface area: 280 acres.
Is Long Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Long Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Long Lake?
- Long Lake typically sits around 74°F at the surface in August, from 11 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Long Lake?
- Long Lake has a maximum depth of 28 feet. The lake covers 280 acres.
What fish are in Long Lake?
- Fish species found in Long Lake include Panfish, Largemouth Bass, Northern Pike, Walleye. Long Lake is located in Bayfield County, Wisconsin.
Does Long Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Long Lake (clouds, ice, or an off-season gap). The most recent reading was high (285,759 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
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 Jackman Lake, Long Lake. Public access is listed as yes.
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Where this data comes from
44 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX44 samples · 2020–2025
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
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