North Lake Deep
North Lake Deep in Cook County, Minnesota has a water quality grade of A (Excellent). Phosphorus: 7.7 µg/L. Chlorophyll-a (algae): 2.9 µg/L.
- Typical in July
- 71°F
- Type
- Oligotrophic
- Trend
- → Stable
Next lake in Cook County
North Lake Deep is a cold, clear oligotrophic lake in Cook County, Minnesota. Water quality is graded A based on 2 sampling years through 2024. Water clarity is declining over recent sampling years. Compared to the 43 other monitored lakes in Cook County, North Lake Deep ranks #34 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-10. Grade methodology: LakeGrade methodology.
Watch North Lake Deep water quality
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Swimming Safety
Grade onlyLimited data
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
No clarity data. Phosphorus level: 7.7 µg/L. Chlorophyll-a: 2.9 µg/L. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 7.7 µg/L | Good |
| Chlorophyll-a (Algae) | 2.9 µg/L | Good |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near North Lake Deep
Compare lakeside cabins, hotels, and vacation rentals near North 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.
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Water Temperature
North Lake Deep typically sits around 71°F at the surface in July. Summer average is about 70°F. Usually warmest in Jul (about 71°F) and coldest in Oct (about 52°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 111 field readings (2010–2024) via the EPA Water Quality Portal. See the full North Lake Deep water temperature breakdown →
Fishing North Lake Deep
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -10.222 m/yr | 4 |
| Phosphorus | ↑ Improving | -2.49 µg/L/yr | 4 |
| Chlorophyll-a | → Stable | -0.03 µg/L/yr | 4 |
County Ranking
Ranked #34 of 44 lakes in Cook County
Nearby Lakes in Cook County
Frequently asked questions about North Lake Deep
What is the water quality grade for North Lake Deep?
- North Lake Deep in Cook County, Minnesota has a water quality grade of A (Excellent). Phosphorus: 7.7 µg/L. Chlorophyll-a (algae): 2.9 µg/L.
Is North Lake Deep safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. North Lake Deep has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.9 µg/L. Always check local health department advisories before swimming.
What is the water temperature of North Lake Deep?
- North Lake Deep typically sits around 71°F at the surface in July, from 111 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
Explore North Lake Deep across LakeGrade
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Where this data comes from
46 measurements from 2 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Grand Portage Reservation
GPC5_WQX25 samples · 2022–2024 - 21GPBCH - Grand Portage Beaches (Tribal)
21GPBCH21 samples · 2020
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
Monitoring station identifiers (2)
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.