Grass Lake
Hennepin County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Grass Lake. Here is what has been measured.
- Eutrophic
Grass Lake in Hennepin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Phosphorus: 112 µg/L. Chlorophyll-a (algae): 20.3 µg/L.
Grass Lake is a productive, nutrient-rich eutrophic lake in Hennepin County, Minnesota. Overall water quality is improving over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 80 other monitored lakes in Hennepin County, Grass Lake ranks #50 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-22. Methodology: how these readings are compared.
What Grass Lake is good for
From access and monitoring records, not editorial picks.
- Ice seasonIce-out around Mar 30
Swimming conditions
Readings onlyAlgae risk
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Grass Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Grass Lake
These are the measurements Minnesota PCA publishes for Grass Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 112 µg/L. Chlorophyll-a 20.3 µg/L. TSI 66.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 112µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 20.3µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 66 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Grass Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Grass Lake typically sits around 58°F at the surface in October. Summer average is about 72°F. Usually warmest in Jul (about 77°F) and coldest in Apr (about 44°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (44°F) to its warmest (77°F).
Typical surface water temperature by month, from 18 field readings (2010–2024) via the EPA Water Quality Portal. See the full Grass Lake water temperature breakdown →
Stays via Stay22
Stays near Grass Lake
Compare lakeside cabins, hotels, and vacation rentals near Grass Lake 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Grass Lake are listed below.
Top-rated places to stay near Grass Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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 →
Follow Grass Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Grass Lake
Water quality readings over time
3 seasons of samples on record (2020–2024). Calling a direction takes at least 4 years of the same measurement.
Phosphorus
Improving-9.37 µg/L/yr3 years
Chlorophyll-a
Improving-6.45 µg/L/yr3 years
Ice season
Typical ice-out
Mar 30
Earliest Mar 4, 2024 · Latest Apr 11, 2023
Most recent ice-out
Mar 4
2024
9 observations · Minnesota PCA ice records
Nearby Lakes in Hennepin County
Frequently asked questions about Grass Lake
Where is Grass Lake?
- Grass Lake is a lake in Hennepin County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Grass Lake?
- Grass Lake in Hennepin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Phosphorus: 112 µg/L. Chlorophyll-a (algae): 20.3 µg/L.
Is Grass Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Grass Lake?
- Grass Lake typically sits around 58°F at the surface in October, from 18 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
When does Grass Lake thaw?
- Grass Lake typically has ice-out around Mar 30.
Can I fish at Grass Lake?
- Public access to Grass Lake is listed as no on the lake record, so confirm before you make the trip. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Grass Lake across LakeQuality
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Hennepin County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Crow River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Grass Lake
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
63 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA63 samples · 2020–2024
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity, Nephelometric Method
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Ice data from Minnesota DNR Climate