Third Lake
Carlton County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Third Lake. Here is what has been measured.
- Mesotrophic
Third Lake in Carlton County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.5 ft visibility. Phosphorus: 21.5 µg/L. Chlorophyll-a (algae): 2.3 µg/L.
Third Lake is a mesotrophic lake in Carlton County, Minnesota. Water clarity is improving over recent sampling years. Compared to the 21 other monitored lakes in Carlton County, Third Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-15. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLow algae
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 Third 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 Third Lake
These are the measurements Minnesota PCA publishes for Third Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 8.5 ft. Phosphorus 21.5 µg/L. Chlorophyll-a 2.3 µg/L. TSI 44.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 21.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.3µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 44 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Third Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Third Lake typically sits around 53°F at the surface in October. Summer average is about 65°F. Usually warmest in Jul (about 73°F) and coldest in May (about 50°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (50°F) to its warmest (73°F).
Typical surface water temperature by month, from 253 field readings (2010–2021) via the EPA Water Quality Portal. See the full Third Lake water temperature breakdown →
Stays via Stay22
Stays near Third Lake
Compare lakeside cabins, hotels, and vacation rentals near Third Lake in Carlton 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 Third 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 Third Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Third Lake
Water Quality Trend: Stable
Based on 5 years of monitoring (2020–2024).
Water clarity
Improving5 years
Phosphorus
Worsening+20.9 µg/L/yr4 years
Chlorophyll-a
Stable0 µg/L/yr5 years
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Third Lake under Clean Water Act (NPDES) discharge permits.
- Fond Du Lac Band Of Lake SuperiorCloquet · 0.7 mi away · NPDES MN0075017
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in Carlton County
Frequently asked questions about Third Lake
Where is Third Lake?
- Third Lake is a lake in Carlton County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Third Lake?
- Third Lake in Carlton County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.5 ft visibility. Phosphorus: 21.5 µg/L. Chlorophyll-a (algae): 2.3 µg/L.
Is Third 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 Third Lake?
- Third Lake typically sits around 53°F at the surface in October, from 253 EPA Water Quality Portal field readings (2010–2021). That is a typical value for the month, not a live reading.
Explore Third Lake across LakeQuality
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Carlton County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Third Lake
Other Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Where this data comes from
341 measurements from 5 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Fond du Lac Band of Chippewa (MN)
FONDULAC_WQX341 samples · 2020–2024
Analytical methods
- 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
- Color, APHA Platinum-Cobalt
- For determination of Copper by the Bicinchoninate method.
Monitoring station identifiers (5)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)