Franklin Lake
Franklin Lake in Forest County, Wisconsin has a water quality grade of B (Good). Water clarity: 16 ft visibility. Phosphorus: 11.3 µg/L. Maximum depth: 46 ft. Surface area: 839 acres.
- Clarity
- 16 ft
- Typical in August
- 74°F
- Max depth
- 46 ft
- Area
- 839 acres
- Type
- Oligotrophic
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Forest County
Franklin Lake is a 839-acre cold, clear oligotrophic lake in Forest County, Wisconsin with a maximum depth of 46 feet. Water quality is graded B based on 1 sampling years through 2026. Overall water quality is declining over recent sampling years. The lake supports 5 documented fish species including Panfish, Largemouth Bass, and Smallmouth Bass. Public access is available with 1 public boat landing. Compared to the 22 other monitored lakes in Forest County, Franklin Lake ranks #14 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-05-07. 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)
Crystal clear, you can see 16 ft down. Phosphorus level: 11.3 µg/L. Trophic State Index: 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16 ft | Not graded |
| Phosphorus | 11.3 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Franklin Lake
Compare lakeside cabins, hotels, and vacation rentals near Franklin Lake in Forest 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
Franklin Lake typically sits around 74°F at the surface in August. Summer average is about 71°F. Usually warmest in Jul (about 74°F) and coldest in May (about 55°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 14 field readings (2024–2025) via the EPA Water Quality Portal. See the full Franklin Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Franklin Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (48,753 cells/mL) on July 6, 2026.
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 | 46 ft |
| Surface Area | 839 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Franklin LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Franklin 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. 2 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Franklin 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).
- 2025Franklin Lake comprehensive survey, 2025Comprehensive Survey · WI DNR · 2025 (PDF)
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.086 m/yr | 6 |
| Phosphorus | ↓ Declining | +2.53 µg/L/yr | 6 |
County Ranking
Ranked #14 of 23 lakes in Forest County
Nearby Lakes in Forest County
Frequently asked questions about Franklin Lake
What is the water quality grade for Franklin Lake?
- Franklin Lake in Forest County, Wisconsin has a water quality grade of B (Good). Water clarity: 16 ft visibility. Phosphorus: 11.3 µg/L. Maximum depth: 46 ft. Surface area: 839 acres.
Is Franklin Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Franklin Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Franklin Lake?
- Franklin Lake typically sits around 74°F at the surface in August, from 14 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Franklin Lake?
- Franklin Lake has a maximum depth of 46 feet. The lake covers 839 acres.
What fish are in Franklin Lake?
- Fish species found in Franklin Lake include Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Franklin Lake is located in Forest County, Wisconsin.
Does Franklin Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Franklin Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (48,753 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Are there boat ramps on Franklin Lake?
- Franklin Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Franklin Lake. Public access is listed as yes.
Explore Franklin Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Wisconsin
Fish species and best lakes in Forest County
Species activity outlook by water temperature and season
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Where to stay at Wisconsin's top lakes, each with its grade
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Low nutrients, clear water, excellent for swimming
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Where this data comes from
63 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_WQX63 samples · 2020–2026
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
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