Little Thunder Lake
Little Thunder Lake in Beltrami County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 2.8 µg/L.
- Clarity
- 15 ft
- Typical in August
- 73°F
- Type
- Oligotrophic
- Trend
- ↓ Declining
Next lake in Beltrami County
Little Thunder Lake is a cold, clear oligotrophic lake in Beltrami County, Minnesota. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. Compared to the 84 other monitored lakes in Beltrami County, Little Thunder Lake ranks #52 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-10. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Crystal clear, you can see 15 ft down. Phosphorus level: 12 µg/L. Chlorophyll-a: 2.8 µg/L. Trophic State Index: 40.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15 ft | Not graded |
| Phosphorus | 12 µg/L | Good |
| Chlorophyll-a (Algae) | 2.8 µg/L | Good |
| Trophic State Index (TSI) | 40 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Little Thunder Lake
Compare lakeside cabins, hotels, and vacation rentals near Little Thunder 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 Little Thunder Lake
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Water Temperature
Little Thunder Lake typically sits around 73°F at the surface in August. Summer average is about 74°F. Usually warmest in Jul (about 77°F) and coldest in Feb (about 37°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 65 field readings (2011–2025) via the EPA Water Quality Portal. See the full Little Thunder Lake water temperature breakdown →
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fishing Little Thunder Lake
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.357 m/yr | 6 |
| Phosphorus | → Stable | -0.16 µg/L/yr | 6 |
| Chlorophyll-a | → Stable | +0.05 µg/L/yr | 6 |
County Ranking
Ranked #52 of 85 lakes in Beltrami County
Nearby Lakes in Beltrami County
Frequently asked questions about Little Thunder Lake
What is the water quality grade for Little Thunder Lake?
- Little Thunder Lake in Beltrami County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 2.8 µg/L.
Is Little Thunder Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Little Thunder Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.8 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Little Thunder Lake?
- Little Thunder Lake typically sits around 73°F at the surface in August, from 65 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Little Thunder Lake?
- The available depth estimate for Little Thunder Lake is shallower than its measured water clarity, which cannot be right, so no depth is shown.
Explore Little Thunder Lake across LakeGrade
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Where this data comes from
98 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Red Lake DNR
REDLAKE_WQX98 samples · 2020–2025
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 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.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)