Grass Island Lake
Grass Island Lake in Beltrami County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar.
- Typical in August
- 69°F
- Trend
- ↑ Improving
Next lake in Beltrami County
Why Grass Island Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Grass Island Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Grass Island Lake is a lake in Beltrami County, Minnesota. Overall water quality is improving over recent sampling years.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2020-03-03. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Grass Island Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
No clarity data.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples |
Where to stay near Grass Island Lake
Compare lakeside cabins, hotels, and vacation rentals near Grass Island Lake in Beltrami 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 Grass Island Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Grass Island Lake typically sits around 69°F at the surface in August. Summer average is about 73°F. Usually warmest in Jul (about 79°F) and coldest in Sep (about 62°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 13 field readings (2016–2019) via the EPA Water Quality Portal. See the full Grass Island Lake water temperature breakdown →
Fishing Grass Island Lake
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.186 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.57 µg/L/yr | 6 |
| Chlorophyll-a | → Stable | +0.01 µg/L/yr | 6 |
Graded lakes near Grass Island Lake
Grass Island Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Beltrami County
Frequently asked questions about Grass Island Lake
What is the water quality grade for Grass Island Lake?
- Grass Island Lake in Beltrami County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar.
Is Grass Island Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Grass Island Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of Grass Island Lake?
- Grass Island Lake typically sits around 69°F at the surface in August, from 13 EPA Water Quality Portal field readings (2016–2019). That is a typical value for the month, not a live reading.
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Where this data comes from
2 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Red Lake DNR
REDLAKE_WQX2 samples · 2020
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- Turbidity by Nephelometry
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.