Mayhew Lake
Cook County, Minnesota221 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Mayhew Lake. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- 84 ft max depth
- Public access
Mayhew Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 20.6 ft visibility. Phosphorus: 5 µg/L. Chlorophyll-a (algae): 1.5 µg/L. Maximum depth: 84 ft. Surface area: 220.9 acres.
Minnesota DNR's Standard Survey on July 8, 2023 caught 0.50 northern pike per trap net at Mayhew Lake. DNR survey details →
Mayhew Lake is a 221-acre cold, clear oligotrophic lake in Cook County, Minnesota with a maximum depth of 84 feet (33-foot average). Overall water quality is improving over recent sampling years. The lake supports 8 documented fish species including bluegill, green sunfish, and hybrid sunfish. Public access is available. Compared to the 43 other monitored lakes in Cook County, Mayhew Lake ranks #18 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-08-20. Methodology: how these readings are compared.
Mayhew Lake covers about 220 acres in Cook County. For a place on the water, look through cabin and lake-house rentals near Mayhew Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Mayhew Lake is good for
From access and monitoring records, not editorial picks.
- Clear water20.6 ft of visibility
- Fishing8 species recorded
- Deep water84 ft surveyed max depth
Swimming conditions
Readings onlyLow 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. Mayhew Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Mayhew 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 Mayhew Lake
These are the measurements Minnesota PCA publishes for Mayhew 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 20.6 ft down. Phosphorus 5 µg/L. Chlorophyll-a 1.5 µg/L. TSI 32.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 20.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.5µg/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. | 32 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Mayhew Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Mayhew Lake typically sits around 55°F at the surface in September. Summer average is about 55°F. Usually warmest in Jun (about 56°F) and coldest in Jul (about 54°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (54°F) to its warmest (56°F).
Typical surface water temperature by month, from 300 field readings (2011–2024) via the EPA Water Quality Portal. See the full Mayhew Lake water temperature breakdown →
Minnesota DNR's Standard Survey on July 8, 2023 caught 0.50 northern pike per trap net at Mayhew Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mayhew Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
6 surveys on file from MN DNR Fisheries. Most recent: 2023-07-08 (Standard Survey).
6 surveys on file · most recent 2023-07-08 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Yellow Perch | 26.76 | 2–7 in 2023-07-08 | 0.09 lb |
| Bluegill | 4.87 | 3 in 2023-07-08 | 0.05 lb |
| White Sucker | 4.04 | 9–19 in 2023-07-08 | 1.3 lb |
| Bluntnose Minnow | 3.88 | ||
| Lake Trout | 2.94 | 8–26 in 2023-07-08 | 1.35 lb |
| Rainbow Trout | 1.83 | 11–13 in 2023-07-08 | 0.81 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.
Yellow Perch
Bluegill
White Sucker
Lake Trout
From the 2023-07-08 survey
Mayhew Lake is a 220-acre lake located 35 miles north of Grand Marais. It lies in the headwaters of the Rainy River, draining to that system via Loon, Crab, and Gunflint Lakes into the Granite River. There is a public carry-in access on the southeast corner of the lake. Mayhew Lake has been managed primarily for lake…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Mayhew Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — MayhewFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Mayhew (1833)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — MayhewFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — MayhewPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
84 ft
Average depth
32.5 ft
Surface area
221 acres
Shoreline
5 mi
Littoral zone
15%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,808 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Mayhew Lake
Compare lakeside cabins, hotels, and vacation rentals near Mayhew 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 Mayhew Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Fish Species
Click a species to see every lake where it is documented.
Fishing Mayhew Lake
Water Quality Trend: Improving
Based on 5 years of monitoring (2020–2024).
Water clarity
Stable5 years
Phosphorus
Improving-0.15 µg/L/yr5 years
Chlorophyll-a
Improving-0.06 µg/L/yr5 years
EPA Impairment Status
Mayhew Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN16-0337-00 · Official waterbody report
Nearby Lakes in Cook County
Frequently asked questions about Mayhew Lake
Where is Mayhew Lake?
- Mayhew 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 Mayhew Lake?
- Mayhew Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 20.6 ft visibility. Phosphorus: 5 µg/L. Chlorophyll-a (algae): 1.5 µg/L. Maximum depth: 84 ft. Surface area: 220.9 acres.
Is Mayhew Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Mayhew Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Mayhew Lake?
- Mayhew Lake typically sits around 55°F at the surface in September, from 300 EPA Water Quality Portal field readings (2011–2024). That is a typical value for the month, not a live reading.
How deep is Mayhew Lake?
- Mayhew Lake has a maximum depth of 84 feet and an average depth of 32.5 feet. The lake covers 220.9 acres.
What fish are in Mayhew Lake?
- Fish species found in Mayhew Lake include bluegill, green sunfish, hybrid sunfish, lake trout, northern pike, rainbow trout, white sucker, yellow perch. Mayhew Lake is located in Cook County, Minnesota.
What did the DNR fisheries survey find at Mayhew Lake?
- Minnesota DNR's Standard Survey on July 8, 2023 caught 0.50 northern pike per trap net at Mayhew Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mayhew Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Mayhew Lake?
- Public access to Mayhew Lake is listed as yes on the lake record. 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 Mayhew 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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Where this data comes from
51 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA51 samples · 2020–2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder