Linn Lake
Linn Lake in Chisago County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 2 ft visibility. Phosphorus: 68.5 µg/L. Chlorophyll-a (algae): 43.4 µg/L. Maximum depth: 15 ft. Surface area: 176.99 acres.
- Clarity
- 2 ft
- Typical in August
- 74°F
- Max depth
- 15 ft
- Area
- 177 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- No
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Linn Lake →
Next lake in Chisago County
Linn Lake is a 177-acre productive, nutrient-rich eutrophic lake in Chisago County, Minnesota with a maximum depth of 15 feet (6-foot average). Water quality is graded F based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 29 other monitored lakes in Chisago County, Linn Lake ranks #30 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 onlyAlgae risk
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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Very murky, less than 2 ft of visibility. Phosphorus level: 68.5 µg/L. Chlorophyll-a: 43.4 µg/L. Trophic State Index: 67.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2 ft | Not graded |
| Phosphorus | 68.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 43.4 µg/L | Poor |
| Trophic State Index (TSI) | 67 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Linn Lake
Compare lakeside cabins, hotels, and vacation rentals near Linn Lake in Chisago 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 Linn Lake are listed below.
Top-rated places to stay near Linn Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Linn Lake typically sits around 74°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 78°F) and coldest in May (about 66°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 41 field readings (2011–2025) via the EPA Water Quality Portal. See the full Linn Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 15 ft |
| Average Depth | 6 ft |
| Surface Area | 177 acres |
| Shoreline Length | 3.2 mi |
| Littoral Zone | 100% |
| Public Access | No |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fishing Linn Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1978-08-21 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 245.34 | 0.12 lb |
| Brown Bullhead | 46.59 | 0.26 lb |
| Bluegill | 20.33 | 0.38 lb |
| Hybrid Sunfish | 13.75 | 0.31 lb |
| Northern Pike | 8.41 | 0.74 lb |
| Pumpkinseed | 1.67 | 0.38 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
From the 1978-08-21 survey
When compared to respective state medians, the present fish population status of Linn Lake is as follows. The Blk Bullhead was extremely high at 164 times the state median and the Brn Blhd was very high at 52 times the median. The N Pike was very high at 13.50 per set or 5 times the median and ranged from 11 to 16…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Linn Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — LinnFisheries 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 | ↓ Declining | -0.099 m/yr | 6 |
| Phosphorus | ↓ Declining | +1.5 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -2.31 µg/L/yr | 6 |
EPA Impairment Status
Linn 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 MN13-0014-00 · Official waterbody report
County Ranking
Ranked #30 of 30 lakes in Chisago County
Nearby Lakes With Higher Grades
Linn Lake holds Grade F. 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 Chisago County
Frequently asked questions about Linn Lake
What is the water quality grade for Linn Lake?
- Linn Lake in Chisago County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 2 ft visibility. Phosphorus: 68.5 µg/L. Chlorophyll-a (algae): 43.4 µg/L. Maximum depth: 15 ft. Surface area: 176.99 acres.
Is Linn Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Linn Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 43.4 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Linn Lake?
- Linn Lake typically sits around 74°F at the surface in August, from 41 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Linn Lake?
- Linn Lake has a maximum depth of 15 feet and an average depth of 6 feet. The lake covers 176.99 acres.
Explore Linn Lake across LakeGrade
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Where this data comes from
93 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA93 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
- 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