Lake of the Isles
Lake of the Isles in Hennepin County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 5.2 ft visibility. Phosphorus: 53 µg/L. Chlorophyll-a (algae): 12.9 µg/L. Maximum depth: 31 ft. Surface area: 114.2 acres.
- Clarity
- 5.2 ft
- Typical in August
- 63°F
- Max depth
- 31 ft
- Area
- 114 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- No
- Ice-out
- Apr 6
- Open water
- 237 days
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Lake of the Isles →
Next lake in Hennepin County
Lake of the Isles is a 114-acre productive, nutrient-rich eutrophic lake in Hennepin County, Minnesota with a maximum depth of 31 feet. Water quality is graded D based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 14 documented fish species including black bullhead, black crappie, and bluegill. No public access — the lake is private or restricted. Compared to the 80 other monitored lakes in Hennepin County, Lake of the Isles ranks #43 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-20. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyBacteria A
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.
Based on E. coli testing, Lake of the Isles never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 6 samples across 6 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Minnesota’s current beach and health-department advisories before swimming.
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 5.2 ft. Phosphorus level: 53 µg/L. Chlorophyll-a: 12.9 µg/L. Trophic State Index: 57.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.2 ft | Not graded |
| Phosphorus | 53 µg/L | Poor |
| Chlorophyll-a (Algae) | 12.9 µg/L | Fair |
| Trophic State Index (TSI) | 57 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake of the Isles
Compare lakeside cabins, hotels, and vacation rentals near Lake of the Isles in Hennepin 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Lake of the Isles are listed below.
Top-rated places to stay near Lake of the Isles
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Lake of the Isles typically sits around 63°F at the surface in August. Summer average is about 62°F. Usually warmest in Jul (about 63°F) and coldest in Jan (about 37°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 1,192 field readings (2010–2025) via the EPA Water Quality Portal. See the full Lake of the Isles water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 31 ft |
| Surface Area | 114 acres |
| Shoreline Length | 3.4 mi |
| Littoral Zone | 78% |
| Public Access | No |
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 Lake of the Isles
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Source: USGS Nonindigenous Aquatic Species (NAS) Database. Hover a chip to see scientific name, ecological context, status, and first-observed year.
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2024-07-01 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 44.77 | 0.1 lb |
| Black Crappie | 6.95 | 0.16 lb |
| Black Bullhead | 5.22 | 0.52 lb |
| Yellow Perch | 2.86 | 0.1 lb |
| Northern Pike | 2.18 | 3.67 lb |
| GOS | 1.85 | 0.08 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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.
Bluegill
Black Crappie
Black Bullhead
Yellow Perch
From the 2024-07-01 survey
Lake of the Isles is a 112 acre lake located in the Minneapolis Chain of Lakes. The lake has a maximum depth of 31 feet, but the majority of the lake is less than 15 feet deep. Vegetation can be very abundant in Lake of the Isles, which may create challenges for angling. Lake of the Isles is not stocked, however…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Lake of the Isles. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Lake of the IslesFisheries Lake Survey · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.014 m/yr | 6 |
| Phosphorus | → Stable | +0.56 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +0.49 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (235 observations).
Estimated open water season: 237 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-04 (2024) | 2018-04-30 (2018) |
| Ice-In | 1991-11-05 (1991) | 2024-01-16 (2024) |
Most recent ice-out: 2026-03-30
EPA Impairment Status
Lake of the Isles is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN27-0040-00 · Official waterbody report
County Ranking
Ranked #43 of 81 lakes in Hennepin County
Nearby Lakes With Higher Grades
Lake of the Isles holds Grade D. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Hennepin County
Frequently asked questions about Lake of the Isles
What is the water quality grade for Lake of the Isles?
- Lake of the Isles in Hennepin County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 5.2 ft visibility. Phosphorus: 53 µg/L. Chlorophyll-a (algae): 12.9 µg/L. Maximum depth: 31 ft. Surface area: 114.2 acres.
Is Lake of the Isles safe to swim in?
- Based on E. coli testing, Lake of the Isles never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 6 samples across 6 seasons. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Lake of the Isles has a water quality grade of D (Nutrient-rich). Bacteria levels can spike quickly after heavy rain, so always check Minnesota's current beach and health-department advisories before you swim.
What is the water temperature of Lake of the Isles?
- Lake of the Isles typically sits around 63°F at the surface in August, from 1,192 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Lake of the Isles?
- Lake of the Isles has a maximum depth of 31 feet. The lake covers 114.2 acres.
What fish are in Lake of the Isles?
- Fish species found in Lake of the Isles include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, yellow bullhead, yellow perch. Lake of the Isles is located in Hennepin County, Minnesota.
When does Lake of the Isles thaw?
- Lake of the Isles typically has ice-out around Apr 6. Ice typically forms around Nov 29. The open water season is approximately 237 days.
Explore Lake of the Isles across LakeGrade
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Where this data comes from
798 measurements from 3 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
MNPCA798 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity, Nephelometric Method
- Turbidity, Probe Method
Monitoring station identifiers (3)
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
Ice data from Minnesota DNR Climate