Gunflint Lake
Cook County, Minnesota4,009 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Gunflint Lake. Here is what has been measured.
- Oligotrophic
- spiny waterflea
- 200 ft max depth
- Public access
- Limited data
Gunflint Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 16.5 ft visibility. Phosphorus: 5.5 µg/L. Chlorophyll-a (algae): 2.6 µg/L. Maximum depth: 200 ft. Surface area: 4009.12 acres.
Minnesota DNR's Targeted Survey on August 7, 2023 caught 4.62 walleye per gill net at Gunflint Lake. Length samples in the latest survey that recorded them ran 8–27 inches. DNR survey details →
Gunflint Lake is a 4,009-acre cold, clear oligotrophic lake in Cook County, Minnesota with a maximum depth of 200 feet. Overall water quality is declining over recent sampling years. The lake supports 12 documented fish species including bluegill, burbot, and cisco species. Public access is available with 1 public boat landing. Compared to the 43 other monitored lakes in Cook County, Gunflint Lake ranks #20 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-23. Methodology: how these readings are compared.
What Gunflint Lake is good for
From access and monitoring records, not editorial picks.
- Clear water16.5 ft of visibility
- Boat launch1 documented ramp
- Fishing12 species recorded
- Ice seasonIce-out around May 6
- Deep water200 ft surveyed max depth
- Big water4,009 acres
Swimming conditions
Readings onlyLimited data
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 Gunflint Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Gunflint Lake
These are the measurements Minnesota PCA publishes for Gunflint Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 16.5 ft down. Phosphorus 5.5 µg/L. Chlorophyll-a 2.6 µg/L. TSI 35.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 16.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 5.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.6µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 35 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Gunflint Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Gunflint Lake typically sits around 58°F at the surface in September. Summer average is about 56°F. Usually warmest in Sep (about 58°F) and coldest in May (about 45°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (45°F) to its warmest (58°F).
Typical surface water temperature by month, from 181 field readings (2024–2025) via the EPA Water Quality Portal. See the full Gunflint Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on August 7, 2023 caught 4.62 walleye per gill net at Gunflint Lake. Length samples in the latest survey that recorded them ran 8–27 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Gunflint Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
13 surveys on file from MN DNR Fisheries. Most recent: 2025-08-11 (Targeted Survey).
13 surveys on file · most recent 2025-08-11 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Rock Bass | 4.78 | 3–10 in 2023-08-07 | 0.32 lb |
| Walleye | 3.96 | 8–27 in 2023-08-07 | 1.4 lb |
| Tullibee (Cisco) | 3.42 | 3–10 in 2023-08-07 | 0.22 lb |
| White Sucker | 2.03 | 7–18 in 2023-08-07 | 2.29 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Rock Bass
Walleye
Tullibee (Cisco)
White Sucker
From the 2025-08-11 survey
Temperature and dissolved oxygen measurements were collected from the deepest basin in Gunflint Lake on August 11th, 2025. This was done to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Trout, the most sensitive coldwater species present in this lake (Cisco,…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Gunflint Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — GunflintFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Gunflint (1800)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — GunflintFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — GunflintPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
200 ft
Surface area
4,009 acres
Shoreline
39.2 mi
Littoral zone
17%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
147 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,539 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Gunflint 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 Gunflint Lake
Compare lakeside cabins, hotels, and vacation rentals near Gunflint Lake in Cook County, Minnesota — 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 Gunflint Lake
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Follow Gunflint Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Gunflint 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: Worsening
Based on 5 years of monitoring (2020–2025).
Water clarity
Worsening5 years
Ice season
Typical ice-out
May 6
Earliest Mar 23, 2012 · Latest Jun 3, 1936
Typical ice-in
Dec 9
Earliest Nov 27, 2002 · Latest Dec 23, 2001
Most recent ice-out
May 12
2023
87 observations · Minnesota PCA ice records
Nearby Lakes in Cook County
Frequently asked questions about Gunflint Lake
Where is Gunflint Lake?
- Gunflint Lake is a lake in Cook County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Gunflint Lake?
- Gunflint Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 16.5 ft visibility. Phosphorus: 5.5 µg/L. Chlorophyll-a (algae): 2.6 µg/L. Maximum depth: 200 ft. Surface area: 4009.12 acres.
Is Gunflint 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 Gunflint Lake?
- Gunflint Lake typically sits around 58°F at the surface in September, from 181 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Gunflint Lake?
- Gunflint Lake has a maximum depth of 200 feet. The lake covers 4009.12 acres.
What fish are in Gunflint Lake?
- Fish species found in Gunflint Lake include bluegill, burbot, cisco species, lake trout, northern pike, rainbow smelt, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow perch. Gunflint Lake is located in Cook County, Minnesota.
What did the DNR fisheries survey find at Gunflint Lake?
- Minnesota DNR's Targeted Survey on August 7, 2023 caught 4.62 walleye per gill net at Gunflint Lake. Length samples in the latest survey that recorded them ran 8–27 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Gunflint Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Gunflint Lake thaw?
- Gunflint Lake typically has ice-out around May 6. Ice typically forms around Dec 9. The open water season is approximately 217 days.
Are there boat ramps on Gunflint Lake?
- Gunflint Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Gunflint Lake. Public access is listed as yes.
Can I fish at Gunflint Lake?
- Gunflint 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 Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Gunflint Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Cook County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
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Compare Gunflint Lake With Nearby Lakes
Where this data comes from
32 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA32 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate