Green Lake
Green Lake in Chisago County, Minnesota has a water quality grade of C (Fair). Water clarity: 6 ft visibility. Phosphorus: 23 µg/L. Chlorophyll-a (algae): 8.4 µg/L. Maximum depth: 32 ft. Surface area: 1809.49 acres.
- Clarity
- 6 ft
- Typical in August
- 75°F
- Max depth
- 32 ft
- Area
- 1,809 acres
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Mar 31
Next lake in Chisago County
Green Lake is a 1,809-acre productive, nutrient-rich eutrophic lake in Chisago County, Minnesota with a maximum depth of 32 feet (9-foot average). Water quality is graded C based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 15 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 29 other monitored lakes in Chisago County, Green Lake ranks #13 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-04. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyModerate
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)
Murky, only visible to about 6 ft. Phosphorus level: 23 µg/L. Chlorophyll-a: 8.4 µg/L. Trophic State Index: 51.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6 ft | Not graded |
| Phosphorus | 23 µg/L | Good |
| Chlorophyll-a (Algae) | 8.4 µg/L | Fair |
| Trophic State Index (TSI) | 51 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Green Lake
Compare lakeside cabins, hotels, and vacation rentals near Green 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.
Top-rated places to stay near Green Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Green Lake typically sits around 75°F at the surface in August. Summer average is about 75°F. Usually warmest in Jul (about 77°F) and coldest in May (about 62°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 84 field readings (2010–2025) via the EPA Water Quality Portal. See the full Green Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Green Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (118,032 cells/mL) on May 16, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 32 ft |
| Average Depth | 9 ft |
| Surface Area | 1,809 acres |
| Shoreline Length | 16.5 mi |
| Littoral Zone | 68% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Little Green LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Green 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
10 surveys on file from MN DNR Fisheries. Most recent: 2023-07-24 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 40.20 | 0.1 lb |
| Bluntnose Minnow | 30.03 | — |
| SUN | 25.89 | — |
| SFS | 24.06 | — |
| Largemouth Bass | 20.06 | 0.94 lb |
| BKF | 12.30 | — |
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
Largemouth Bass
From the 2023-07-24 survey
Green Lake is the largest lake (1,714 acres) in the Chisago City area. It has three distinct basins: the north end, which is commonly called Little Green, the large windswept main basin, and the southern end, which consists of shallow bays with abundant vegetation. Green and blue-green algae are common in the summer,…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Green Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — GreenFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — GreenFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — GreenPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.004 m/yr | 6 |
| Phosphorus | ↑ Improving | -2.84 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -5.23 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (14 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-03 (2024) | 2022-04-18 (2022) |
| Ice-In | 1999-12-17 (1999) | 1999-12-17 (1999) |
Most recent ice-out: 2026-04-01
EPA Impairment Status
Green Lake 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 MN13-0041-01 · Official waterbody report · Matched by proximity (1.24 km)
County Ranking
Ranked #13 of 30 lakes in Chisago County
Nearby Lakes With Higher Grades
Green Lake holds Grade C. 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 Green Lake
What is the water quality grade for Green Lake?
- Green Lake in Chisago County, Minnesota has a water quality grade of C (Fair). Water clarity: 6 ft visibility. Phosphorus: 23 µg/L. Chlorophyll-a (algae): 8.4 µg/L. Maximum depth: 32 ft. Surface area: 1809.49 acres.
Is Green Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Green Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 8.4 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Green Lake?
- Green Lake typically sits around 75°F at the surface in August, from 84 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Green Lake?
- Green Lake has a maximum depth of 32 feet and an average depth of 9 feet. The lake covers 1809.49 acres.
What fish are in Green Lake?
- Fish species found in Green Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Green Lake is located in Chisago County, Minnesota.
When does Green Lake thaw?
- Green Lake typically has ice-out around Mar 31.
Does Green Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Green Lake (clouds, ice, or an off-season gap). The most recent reading was high (118,032 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Green Lake?
- Green Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Little Green Lake. Public access is listed as yes.
Explore Green Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Chisago County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the St. Croix Watershed, ranked by water quality
High nutrients, frequent algae, reduced clarity
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
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Other Grade C Lakes in Minnesota
Eutrophic Lakes in Minnesota
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Where this data comes from
328 measurements from 4 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
MNPCA328 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 (4)
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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate