Jack Lake
Jack Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15.7 ft visibility. Phosphorus: 9 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Maximum depth: 110 ft. Surface area: 141.97 acres.
- Clarity
- 15.7 ft
- Typical in August
- 49°F
- Max depth
- 110 ft
- Area
- 142 acres
- Type
- Oligotrophic
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Cass County
Jack Lake is a 142-acre cold, clear oligotrophic lake in Cass County, Minnesota with a maximum depth of 110 feet. Water quality is graded A based on 3 sampling years through 2024. Overall water quality is declining over recent sampling years. The lake supports 13 documented fish species including black crappie, bluegill, and bowfin (dogfish). Public access is available with 4 public boat landings. Compared to the 103 other monitored lakes in Cass County, Jack Lake ranks #83 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-16. 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 15.7 ft down. Phosphorus level: 9 µg/L. Chlorophyll-a: 3.1 µg/L. Trophic State Index: 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.7 ft | Not graded |
| Phosphorus | 9 µg/L | Good |
| Chlorophyll-a (Algae) | 3.1 µg/L | Good |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Jack Lake
Compare lakeside cabins, hotels, and vacation rentals near Jack Lake in Cass 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.
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Water Temperature
Jack Lake typically sits around 49°F at the surface in August. Summer average is about 48°F. Usually warmest in Aug (about 49°F) and coldest in May (about 44°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 501 field readings (2011–2024) via the EPA Water Quality Portal. See the full Jack Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 110 ft |
| Surface Area | 142 acres |
| Shoreline Length | 2.5 mi |
| Littoral Zone | 31% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Jack LakePublic
- Horseshoe Bay LodgeSemi-private
- Big Rock LodgeSemi-private
- Northland ResortSemi-private
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Jack Lake
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2024-08-20 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| CNM | 39.37 | — |
| Bluegill | 21.11 | 0.14 lb |
| BNS | 14.75 | — |
| Tullibee (Cisco) | 6.24 | 0.21 lb |
| LES | 6.18 | — |
| IOD | 4.34 | — |
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
Tullibee (Cisco)
From the 2024-08-20 survey
A targeted survey of nearshore fish species in Jack Lake which is located wholly within the Leech Lake Band of Ojibwe Nation, was conducted August 20-21, 2024, by Index of Biological Integrity (IBI) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Jack Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — JackFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Jack (1498)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — JackPublic 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 | -0.24 m/yr | 2 |
| Phosphorus | ↓ Declining | +3 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -0.9 µg/L/yr | 2 |
County Ranking
Ranked #83 of 104 lakes in Cass County
Nearby Lakes in Cass County
Frequently asked questions about Jack Lake
What is the water quality grade for Jack Lake?
- Jack Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15.7 ft visibility. Phosphorus: 9 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Maximum depth: 110 ft. Surface area: 141.97 acres.
Is Jack Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Jack Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 3.1 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Jack Lake?
- Jack Lake typically sits around 49°F at the surface in August, from 501 EPA Water Quality Portal field readings (2011–2024). That is a typical value for the month, not a live reading.
How deep is Jack Lake?
- Jack Lake has a maximum depth of 110 feet. The lake covers 141.97 acres.
What fish are in Jack Lake?
- Fish species found in Jack Lake include black crappie, bluegill, bowfin (dogfish), hybrid sunfish, largemouth bass, northern pike, northern sunfish, pumpkinseed, rock bass, tullibee (cisco), walleye, yellow bullhead, yellow perch. Jack Lake is located in Cass County, Minnesota.
Are there boat ramps on Jack Lake?
- Jack Lake has 4 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Jack Lake, Horseshoe Bay Lodge, Big Rock Lodge, Northland Resort. Public access is listed as yes.
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Where this data comes from
59 measurements from 2 monitoring stations, 2023–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Leech Lake Band of Ojibwe
LEECHLAK_WQX44 samples · 2023–2024 - Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA15 samples · 2023
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Nitrate-Nitrite Nitrogen by Colorimetry
Monitoring station identifiers (2)
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
Named boat-access points from the USGS National Boat Ramps inventory