Merrill Lake
Merrill Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 16 ft visibility.
- Clarity
- 16 ft
- Typical in August
- 73°F
- Trend
- → Stable
- Public access
- No
- Ice-out
- Apr 30
- Open water
- 206 days
Next lake in St. Louis County
Why Merrill 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 Merrill Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
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.
Merrill Lake is a lake in St. Louis County, Minnesota. Limited fish-species data available. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-24. Grade methodology: LakeGrade methodology.
Watch Merrill Lake water quality
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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 Merrill Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Crystal clear, you can see 16 ft down. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Merrill Lake
Compare lakeside cabins, hotels, and vacation rentals near Merrill Lake in St. Louis 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 Merrill Lake
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Water Temperature
Merrill Lake typically sits around 73°F at the surface in August. Summer average is about 72°F. Usually warmest in Jul (about 74°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 16 field readings (2025–2025) via the EPA Water Quality Portal. See the full Merrill Lake water temperature breakdown →
Fishing Merrill Lake
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.085 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (9 observations).
Estimated open water season: 206 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2015-04-12 (2015) | 2013-05-11 (2013) |
| Ice-In | 2014-11-15 (2014) | 2015-11-28 (2015) |
Most recent ice-out: 2015-04-12
Graded lakes near Merrill Lake
Merrill Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in St. Louis County
Frequently asked questions about Merrill Lake
What is the water quality grade for Merrill Lake?
- Merrill Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 16 ft visibility.
Is Merrill Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Merrill 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 Merrill Lake?
- Merrill Lake typically sits around 73°F at the surface in August, from 16 EPA Water Quality Portal field readings (2025–2025). That is a typical value for the month, not a live reading.
When does Merrill Lake thaw?
- Merrill Lake typically has ice-out around Apr 30. Ice typically forms around Nov 22. The open water season is approximately 206 days.
Explore Merrill Lake across LakeGrade
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Where this data comes from
16 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA16 samples · 2025
Analytical methods
- Field measurement/observation, generic method
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
Ice data from Minnesota DNR Climate