Rat Lake
Rat Lake in Aitkin County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 5.5 ft visibility. Maximum depth: 21 ft. Surface area: 431.3 acres.
- Clarity
- 5.5 ft
- Max depth
- 21 ft
- Area
- 431 acres
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 12
- Open water
- 225 days
Next lake in Aitkin County
Why Rat 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 Rat 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.
Rat Lake is a 431-acre lake in Aitkin County, Minnesota with a maximum depth of 21 feet. Overall water quality is improving over recent sampling years. The lake supports 13 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-11. 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 Rat Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Murky, only visible to about 5.5 ft. Trophic State Index: 53.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Rat Lake
Compare lakeside cabins, hotels, and vacation rentals near Rat Lake in Aitkin 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 Rat Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 21 ft |
| Surface Area | 431 acres |
| Shoreline Length | 4.7 mi |
| Littoral Zone | 90% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Wolds Ferry CrossingPublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Rat Lake
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2022-07-08 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| GOS | 22.65 | — |
| Bluegill | 14.07 | 0.29 lb |
| Yellow Perch | 8.27 | 0.18 lb |
| Largemouth Bass | 6.83 | 1.55 lb |
| Northern Pike | 3.28 | 1.57 lb |
| Black Crappie | 3.03 | 0.35 lb |
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
Yellow Perch
Largemouth Bass
Northern Pike
From the 2022-07-08 survey
A targeted survey of nearshore fish species in Rat Lake was conducted on July 8, 2022 by Aitkin Area Fisheries Staff. Sampling sites were evenly spaced around the lake and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Backpack electrofishing was completed at…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Rat Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — RatFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Rat (0142)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — RatFish Stocking History · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.061 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (8 observations).
Estimated open water season: 225 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2012-03-21 (2012) | 2022-04-29 (2022) |
| Ice-In | 2002-11-18 (2002) | 2012-11-27 (2012) |
Most recent ice-out: 2022-04-29
Graded lakes near Rat Lake
Rat Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Aitkin County
Frequently asked questions about Rat Lake
What is the water quality grade for Rat Lake?
- Rat Lake in Aitkin County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 5.5 ft visibility. Maximum depth: 21 ft. Surface area: 431.3 acres.
Is Rat Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Rat Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Rat Lake?
- Rat Lake has a maximum depth of 21 feet. The lake covers 431.3 acres.
What fish are in Rat Lake?
- Fish species found in Rat Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Rat Lake is located in Aitkin County, Minnesota.
When does Rat Lake thaw?
- Rat Lake typically has ice-out around Apr 12. Ice typically forms around Nov 23. The open water season is approximately 225 days.
Are there boat ramps on Rat Lake?
- Rat Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Wolds Ferry Crossing. Public access is listed as yes.
Explore Rat Lake across LakeGrade
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Where this data comes from
35 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA35 samples · 2020–2025
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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate