Little Iron Lake
Little Iron Lake in Cook County, Minnesota has a water quality grade of A (Excellent). Water clarity: 4.2 ft visibility. Phosphorus: 17.5 µg/L. Chlorophyll-a (algae): 5.5 µg/L. Maximum depth: 18 ft. Surface area: 115.16 acres.
- Clarity
- 4.2 ft
- Typical in August
- 65°F
- Max depth
- 18 ft
- Area
- 115 acres
- Type
- Mesotrophic
- Public access
- Yes
Next lake in Cook County
Little Iron Lake is a 115-acre mesotrophic lake in Cook County, Minnesota with a maximum depth of 18 feet. Water quality is graded A based on 2 sampling years through 2025. The lake supports 7 documented fish species including bluegill, green sunfish, and northern pike. Public access is available. Compared to the 43 other monitored lakes in Cook County, Little Iron Lake ranks #36 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-16. Grade methodology: LakeGrade methodology.
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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)
Murky, only visible to about 4.2 ft. Phosphorus level: 17.5 µg/L. Chlorophyll-a: 5.5 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.2 ft | Not graded |
| Phosphorus | 17.5 µg/L | Good |
| Chlorophyll-a (Algae) | 5.5 µg/L | Good |
| Trophic State Index (TSI) | 50 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Little Iron Lake
Compare lakeside cabins, hotels, and vacation rentals near Little Iron 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.
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Water Temperature
Little Iron Lake typically sits around 65°F at the surface in August. Summer average is about 65°F. Usually warmest in Jul (about 66°F) and coldest in May (about 53°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 37 field readings (2011–2025) via the EPA Water Quality Portal. See the full Little Iron Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 18 ft |
| Surface Area | 115 acres |
| Shoreline Length | 7.5 mi |
| Littoral Zone | 68% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Little Iron Lake
EPA Impairment Status
Little Iron Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN16-0355-00 · Official waterbody report
County Ranking
Ranked #36 of 44 lakes in Cook County
Nearby Lakes in Cook County
Frequently asked questions about Little Iron Lake
What is the water quality grade for Little Iron Lake?
- Little Iron Lake in Cook County, Minnesota has a water quality grade of A (Excellent). Water clarity: 4.2 ft visibility. Phosphorus: 17.5 µg/L. Chlorophyll-a (algae): 5.5 µg/L. Maximum depth: 18 ft. Surface area: 115.16 acres.
Is Little Iron Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Little Iron Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 5.5 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Little Iron Lake?
- Little Iron Lake typically sits around 65°F at the surface in August, from 37 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Little Iron Lake?
- Little Iron Lake has a maximum depth of 18 feet. The lake covers 115.16 acres.
What fish are in Little Iron Lake?
- Fish species found in Little Iron Lake include bluegill, green sunfish, northern pike, rock bass, walleye, white sucker, yellow perch. Little Iron Lake is located in Cook County, Minnesota.
Explore Little Iron Lake across LakeGrade
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Where this data comes from
14 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA14 samples · 2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
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.
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