Long Lake
Florence County, Wisconsin353 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Long Lake. Here is what has been measured.
- Mesotrophic
- 2 aquatic invasives
- 21 ft max depth
- Public access
Long Lake in Florence County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 7.9 ft visibility. Phosphorus: 25.2 µg/L. Maximum depth: 21 ft. Surface area: 353 acres.
Wisconsin DNR lists Panfish as common on Long Lake. DNR survey details →
Long Lake is a 353-acre mesotrophic lake in Florence County, Wisconsin with a maximum depth of 21 feet. Water clarity is improving over recent sampling years. The lake supports 3 documented fish species including Panfish, Largemouth Bass, and Northern Pike. Public access is available with 1 public boat landing. Compared to the 11 other monitored lakes in Florence County, Long Lake ranks #12 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-09-18. Methodology: how these readings are compared.
Long Lake covers about 350 acres in Florence County. It has one public boat landing. For a place on the water, look through cabin and lake-house rentals near Long Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Long Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing3 species recorded
Swimming conditions
Readings onlyModerate 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 Long 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.
Water quality measurements for Long Lake
These are the measurements Wisconsin DNR publishes for Long Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7.9 ft. Phosphorus 25.2 µg/L. TSI 49.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 25.2µg/L | Fair 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. | 49 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Long Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Long Lake typically sits around 71°F at the surface in September. Summer average is about 70°F. Usually warmest in Jul (about 73°F) and coldest in Feb (about 41°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (41°F) to its warmest (73°F).
Typical surface water temperature by month, from 14 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 (691,831 cells/mL) on June 27, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Wisconsin DNR lists Panfish as common on Long Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Long Lake’s water-quality measurements separately, and the water-quality trend over 4 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. Monitored by volunteers since 2007. 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).
- 2023Long Lake comprehensive survey, 2023Comprehensive Survey · WI DNR · 2023 (PDF)
Lake Details
Max depth
21 ft
Surface area
353 acres
Public access
Yes
Listed by Wisconsin DNR
Lake Size & Watershed
Watershed (drainage) area
10 sq mi
HydroLAKES / HydroSHEDS
Shoreline
4.3 mi
HydroLAKES / HydroSHEDS
Elevation
1,506 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Long LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long Lake in Florence 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
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 Long Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
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Fish Species
Click a species to see every 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.
Water Quality Trend: Stable
Based on 4 years of monitoring (2022–2025).
Water clarity
Improving4 years
Phosphorus
Worsening+0.91 µg/L/yr4 years
Nearby Lakes in Florence County
Frequently asked questions about Long Lake
Where is Long Lake?
- Long Lake is a lake in Florence County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Long Lake?
- Long Lake in Florence County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 7.9 ft visibility. Phosphorus: 25.2 µg/L. Maximum depth: 21 ft. Surface area: 353 acres.
Is Long 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 Long Lake?
- Long Lake typically sits around 71°F at the surface in September, 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 Long Lake?
- Long Lake has a maximum depth of 21 feet. The lake covers 353 acres.
What fish are in Long Lake?
- Fish species found in Long Lake include Panfish, Largemouth Bass, Northern Pike. Long Lake is located in Florence County, Wisconsin.
What did the DNR fisheries survey find at Long Lake?
- Wisconsin DNR lists Panfish as common on Long Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Long Lake’s water-quality measurements separately, and the water-quality trend over 4 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
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 (691,831 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 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Long Lake. Public access is listed as yes.
Can I fish at Long Lake?
- Long Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. 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 Long Lake across LakeQuality
Fish species and the cleanest lakes across Wisconsin
Fish species and best lakes in Florence County
Species activity outlook by water temperature and season
Where to stay at Wisconsin's top lakes, each with its readings
Wisconsin's cleanest lakes, ranked on agency measurements
More lakes in Wisconsin
Other Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
32 measurements from 1 monitoring station, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX32 samples · 2022–2025
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (1)
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
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