Hart Lake
Hart Lake in Hubbard County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 4.5 ft visibility. Phosphorus: 45.5 µg/L. Chlorophyll-a (algae): 9.8 µg/L. Maximum depth: 13 ft. Surface area: 226.31 acres.
- Clarity
- 4.5 ft
- Typical in August
- 72°F
- Max depth
- 13 ft
- Area
- 226 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Hart Lake →
Next lake in Hubbard County
Hart Lake is a 226-acre productive, nutrient-rich eutrophic lake in Hubbard County, Minnesota with a maximum depth of 13 feet. Water quality is graded D based on 2 sampling years through 2023. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 67 other monitored lakes in Hubbard County, Hart Lake ranks #68 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-09-28. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyElevated nutrients
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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 4.5 ft. Phosphorus level: 45.5 µg/L. Chlorophyll-a: 9.8 µg/L. Trophic State Index: 56.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.5 ft | Not graded |
| Phosphorus | 45.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 9.8 µg/L | Fair |
| Trophic State Index (TSI) | 56 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Hart Lake
Compare lakeside cabins, hotels, and vacation rentals near Hart Lake in Hubbard 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 grade measures nutrients and algae, not lodging — cabins and rentals around Hart Lake are listed below.
Top-rated places to stay near Hart Lake
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 →
Water Temperature
Hart Lake typically sits around 72°F at the surface in August. Summer average is about 71°F. Usually warmest in Aug (about 72°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 28 field readings (2018–2023) via the EPA Water Quality Portal. See the full Hart Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 13 ft |
| Surface Area | 226 acres |
| Shoreline Length | 2.6 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Hart LakePublic
Fishing Hart Lake
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1977-07-14 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 79.13 | 0.66 lb |
| Yellow Perch | 9.38 | 0.51 lb |
| White Sucker | 1.63 | 1.6 lb |
| Northern Pike | 1.13 | 1.29 lb |
| Walleye | 1.00 | 1.9 lb |
| Pumpkinseed | 0.75 | 0.2 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
From the 1977-07-14 survey
Mostly Bullheads. Bullheads and Yellow Perch higher than statewide average in the net catch. Northern Pike, Walleye and Panfish lower.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Hart Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — HartFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Hart (1255)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — HartPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.067 m/yr | 2 |
| Phosphorus | ↓ Declining | +2.17 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -0.27 µg/L/yr | 2 |
EPA Impairment Status
Hart Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN29-0063-00 · Official waterbody report
County Ranking
Ranked #68 of 68 lakes in Hubbard County
Nearby Lakes With Higher Grades
Hart Lake holds Grade D. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Hubbard County
Frequently asked questions about Hart Lake
What is the water quality grade for Hart Lake?
- Hart Lake in Hubbard County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 4.5 ft visibility. Phosphorus: 45.5 µg/L. Chlorophyll-a (algae): 9.8 µg/L. Maximum depth: 13 ft. Surface area: 226.31 acres.
Is Hart Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Hart Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 9.8 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Hart Lake?
- Hart Lake typically sits around 72°F at the surface in August, from 28 EPA Water Quality Portal field readings (2018–2023). That is a typical value for the month, not a live reading.
How deep is Hart Lake?
- Hart Lake has a maximum depth of 13 feet. The lake covers 226.31 acres.
Are there boat ramps on Hart Lake?
- Hart Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Hart Lake. Public access is listed as yes.
Explore Hart Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
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Species activity outlook by water temperature and season
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Where this data comes from
45 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA45 samples · 2020–2023
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory