Loon Lake
Loon Lake in Waseca County, Minnesota has a water quality grade of C (Fair). Water clarity: 2.5 ft visibility. Phosphorus: 121.5 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 9 ft. Surface area: 124.94 acres.
- Clarity
- 2.5 ft
- Typical in August
- 77°F
- Max depth
- 9 ft
- Area
- 125 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Mar 27
- Open water
- 252 days
Next lake in Waseca County
Loon Lake is a 125-acre productive, nutrient-rich eutrophic lake in Waseca County, Minnesota with a maximum depth of 9 feet. Water quality is graded C based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 7 documented fish species including black bullhead, bluegill, and channel catfish. Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Waseca County, Loon Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-10. Grade methodology: LakeGrade methodology.
Watch Loon Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Very murky, less than 2.5 ft of visibility. Phosphorus level: 121.5 µg/L. Chlorophyll-a: 5.8 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | Not graded |
| Phosphorus | 121.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 5.8 µg/L | Good |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Loon Lake
Compare lakeside cabins, hotels, and vacation rentals near Loon Lake in Waseca 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
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
Loon Lake typically sits around 77°F at the surface in August. Summer average is about 77°F. Usually warmest in Jul (about 82°F) and coldest in May (about 54°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 36 field readings (2022–2025) via the EPA Water Quality Portal. See the full Loon Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 9 ft |
| Surface Area | 125 acres |
| Shoreline Length | 2.2 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Loon LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Loon Lake
DNR Fisheries Survey Summary
12 surveys on file from MN DNR Fisheries. Most recent: 2023-04-19 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 116.33 | 0.18 lb |
| Black Bullhead | 112.22 | 0.25 lb |
| Black Crappie | 53.93 | 0.16 lb |
| Largemouth Bass | 25.90 | 0.86 lb |
| Walleye | 13.47 | 1.92 lb |
| Northern Pike | 6.44 | 1.89 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 Bullhead
Black Crappie
Largemouth Bass
From the 2023-04-19 survey
Three trap nets were set on 19 April 2023 to assess for winterkill. Yellow Perch and Black Bullheads were common and were the only species sampled. Loon Lake appears to have sustained a moderate winterkill.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Loon Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — LoonFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — LoonFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — LoonPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.554 m/yr | 3 |
Ice Season
Historical ice data from Minnesota DNR (41 observations).
Estimated open water season: 252 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-02-27 (2024) | 2018-04-27 (2018) |
| Ice-In | 2024-11-30 (2024) | 2008-01-18 (2008) |
Most recent ice-out: 2026-03-23
EPA Impairment Status
Loon 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 MN81-0015-00 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Loon Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 2 facilities have a reported Clean Water Act violation in the past three years.
- Waseca WwtpWaseca · 1.5 mi away · NPDES MN0020796MajorRecent violation
- Conagra Foods Packaged Foods LlcWaseca · 0.4 mi away · NPDES MN0001686Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #1 of 2 lakes in Waseca County
Nearby Lakes in Waseca County
Frequently asked questions about Loon Lake
What is the water quality grade for Loon Lake?
- Loon Lake in Waseca County, Minnesota has a water quality grade of C (Fair). Water clarity: 2.5 ft visibility. Phosphorus: 121.5 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 9 ft. Surface area: 124.94 acres.
Is Loon Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Loon Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 5.8 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Loon Lake?
- Loon Lake typically sits around 77°F at the surface in August, from 36 EPA Water Quality Portal field readings (2022–2025). That is a typical value for the month, not a live reading.
How deep is Loon Lake?
- Loon Lake has a maximum depth of 9 feet. The lake covers 124.94 acres.
What fish are in Loon Lake?
- Fish species found in Loon Lake include black bullhead, bluegill, channel catfish, hybrid sunfish, largemouth bass, northern pike, yellow perch. Loon Lake is located in Waseca County, Minnesota.
When does Loon Lake thaw?
- Loon Lake typically has ice-out around Mar 27. Ice typically forms around Dec 4. The open water season is approximately 252 days.
Are there boat ramps on Loon Lake?
- Loon Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Loon Lake. Public access is listed as yes.
Explore Loon Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Waseca County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near Loon Lake
Other Grade C Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
33 measurements from 1 monitoring station, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA33 samples · 2022–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate