Mary Lake
Mary Lake in Hubbard County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 18.8 ft visibility. Maximum depth: 48 ft. Surface area: 235.22 acres.
- Clarity
- 18.8 ft
- Typical in August
- 73°F
- Max depth
- 48 ft
- Area
- 235 acres
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 24
- Open water
- 208 days
Next lake in Hubbard County
Why Mary 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 Mary 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.
Mary Lake is a 235-acre lake in Hubbard County, Minnesota with a maximum depth of 48 feet. Overall water quality is improving over recent sampling years. The lake supports 14 documented fish species including black crappie, bluegill, and brown bullhead. Public access is available.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-07. 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 Mary Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Crystal clear, you can see 18.8 ft down. Trophic State Index: 35.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 18.8 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 35 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Mary Lake
Compare lakeside cabins, hotels, and vacation rentals near Mary 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.
Top-rated places to stay near Mary Lake
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Water Temperature
Mary Lake typically sits around 73°F at the surface in August. Summer average is about 73°F. Usually warmest in Jul (about 75°F) and coldest in May (about 61°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 31 field readings (2023–2025) via the EPA Water Quality Portal. See the full Mary Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 48 ft |
| Surface Area | 235 acres |
| Shoreline Length | 3.3 mi |
| Littoral Zone | 17% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Mary Lake
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2023-07-31 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| MMS | 109.84 | — |
| Bluegill | 14.56 | 0.16 lb |
| Green Sunfish | 10.40 | 0.25 lb |
| CNM | 10.20 | — |
| IOD | 7.80 | — |
| Bluntnose Minnow | 7.34 | — |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Bluegill
Green Sunfish
From the 2023-07-31 survey
A temperature-dissolved oxygen profile was collected in the deepest basin on Big LaSalle Lake on July 31, 2023, to evaluate the amount of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee. Based on the profile, the top of the thermocline (i.e., the location in the water…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Mary Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Big LaSalleFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Big LaSalle (1317)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — Big LaSalleFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Big LaSallePublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.437 m/yr | 6 |
| Phosphorus | ↓ Declining | +0.29 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.34 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (14 observations).
Estimated open water season: 208 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 1992-04-15 (1992) | 1996-05-06 (1996) |
| Ice-In | 1991-11-07 (1991) | 1999-12-10 (1999) |
Most recent ice-out: 2018-05-01
Graded lakes near Mary Lake
Mary Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Hubbard County
Frequently asked questions about Mary Lake
What is the water quality grade for Mary Lake?
- Mary Lake in Hubbard County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 18.8 ft visibility. Maximum depth: 48 ft. Surface area: 235.22 acres.
Is Mary Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Mary 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 Mary Lake?
- Mary Lake typically sits around 73°F at the surface in August, from 31 EPA Water Quality Portal field readings (2023–2025). That is a typical value for the month, not a live reading.
How deep is Mary Lake?
- Mary Lake has a maximum depth of 48 feet. The lake covers 235.22 acres.
What fish are in Mary Lake?
- Fish species found in Mary Lake include black crappie, bluegill, brown bullhead, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Mary Lake is located in Hubbard County, Minnesota.
When does Mary Lake thaw?
- Mary Lake typically has ice-out around Apr 24. Ice typically forms around Nov 18. The open water season is approximately 208 days.
Explore Mary Lake across LakeGrade
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Where this data comes from
31 measurements from 1 monitoring station, 2023–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA31 samples · 2023–2025
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate