Loon Lake Deep
Cook County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Loon Lake Deep. Here is what has been measured.
- Mesotrophic
- Limited data
Loon Lake Deep in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Phosphorus: 23 µg/L. Chlorophyll-a (algae): 7.6 µg/L.
Loon Lake Deep is a mesotrophic lake in Cook County, Minnesota. Overall water quality is improving over recent sampling years. Compared to the 43 other monitored lakes in Cook County, Loon Lake Deep ranks #40 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-10-03. Methodology: how these readings are compared.
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 Loon Lake Deep 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 Loon Lake Deep
These are the measurements Minnesota PCA publishes for Loon Lake Deep, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 23 µg/L. Chlorophyll-a 7.6 µg/L. TSI 50.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 23µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 7.6µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 50 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Loon Lake Deep
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Loon Lake Deep typically sits around 53°F at the surface in October. Summer average is about 72°F. Usually warmest in Jun (about 75°F) and coldest in Oct (about 53°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (53°F) to its warmest (75°F).
Typical surface water temperature by month, from 58 field readings (2010–2022) via the EPA Water Quality Portal. See the full Loon Lake Deep water temperature breakdown →
Stays via Stay22
Stays near Loon Lake Deep
Compare lakeside cabins, hotels, and vacation rentals near Loon Lake Deep 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 Loon Lake Deep
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Fishing Loon Lake Deep
Water quality readings over time
2 seasons of samples on record (2020–2022). Calling a direction takes at least 4 years of the same measurement.
Phosphorus
Improving-2 µg/L/yr2 years
Chlorophyll-a
Stable0 µg/L/yr2 years
Nearby Lakes in Cook County
Frequently asked questions about Loon Lake Deep
Where is Loon Lake Deep?
- Loon Lake Deep 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 Loon Lake Deep?
- Loon Lake Deep in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Phosphorus: 23 µg/L. Chlorophyll-a (algae): 7.6 µg/L.
Is Loon Lake Deep 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 Loon Lake Deep?
- Loon Lake Deep typically sits around 53°F at the surface in October, from 58 EPA Water Quality Portal field readings (2010–2022). That is a typical value for the month, not a live reading.
Explore Loon Lake Deep across LakeQuality
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Where this data comes from
29 measurements from 2 monitoring stations, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Grand Portage Reservation
GPC5_WQX15 samples · 2022 - 21GPBCH - Grand Portage Beaches (Tribal)
21GPBCH14 samples · 2020
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
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.