Florence Lake
Florence Lake in Isanti County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 8.9 ft visibility. Maximum depth: 26 ft. Surface area: 135.45 acres.
- Clarity
- 8.9 ft
- Typical in August
- 77°F
- Max depth
- 26 ft
- Area
- 135 acres
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 3
- Open water
- 237 days
Next lake in Isanti County
Why Florence 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 Florence 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.
Florence Lake is a 135-acre lake in Isanti County, Minnesota with a maximum depth of 26 feet. Overall water quality is declining over recent sampling years. The lake supports 15 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 2025-09-29. 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 Florence Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Moderate clarity, visible to about 8.9 ft. Trophic State Index: 46.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.9 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 46 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Florence Lake
Compare lakeside cabins, hotels, and vacation rentals near Florence Lake in Isanti 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 Florence Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Florence Lake typically sits around 77°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 78°F) and coldest in Apr (about 52°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 48 field readings (2024–2025) via the EPA Water Quality Portal. See the full Florence Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 26 ft |
| Surface Area | 135 acres |
| Shoreline Length | 2.2 mi |
| Littoral Zone | 94% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Florence LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Florence Lake
DNR Fisheries Survey Summary
7 surveys on file from MN DNR Fisheries. Most recent: 2025-07-14 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 41.94 | 0.23 lb |
| Bluegill | 29.78 | 0.16 lb |
| Largemouth Bass | 18.98 | 0.68 lb |
| Pumpkinseed | 9.47 | 0.13 lb |
| TPM | 7.95 | — |
| IOD | 7.92 | — |
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.
Black Bullhead
Bluegill
Largemouth Bass
Pumpkinseed
From the 2025-07-14 survey
A targeted survey of the nearshore fish community was conducted by Hinckley fisheries staff on Florence Lake on July 14, 2025. Nearshore sampling captured 15 species of fish: Banded Kilifish, Blacknose Shiner, Bluegill, Bowfin, Central Mudminnow, Golden Shiner, Green Sunfish, Hybrid Sunfish, Iowa Darter, Largemouth…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Florence Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — FlorenceFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Florence (1841)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — FlorenceFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — FlorencePublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.161 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (47 observations).
Estimated open water season: 237 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-02 (2024) | 2013-05-02 (2013) |
| Ice-In | 2019-11-05 (2019) | 2015-12-19 (2015) |
Most recent ice-out: 2025-03-18
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Florence Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 2 facilities have a reported Clean Water Act violation in the past three years.
- Cambridge WwtpCambridge · 1.7 mi away · NPDES MN0020362MajorRecent violation
- Isanti WwtpIsanti · 3.1 mi away · NPDES MN0023795Recent violation
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.
Graded lakes near Florence Lake
Florence Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Isanti County
Frequently asked questions about Florence Lake
What is the water quality grade for Florence Lake?
- Florence Lake in Isanti County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 8.9 ft visibility. Maximum depth: 26 ft. Surface area: 135.45 acres.
Is Florence Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Florence 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 Florence Lake?
- Florence Lake typically sits around 77°F at the surface in August, from 48 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Florence Lake?
- Florence Lake has a maximum depth of 26 feet. The lake covers 135.45 acres.
What fish are in Florence Lake?
- Fish species found in Florence Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Florence Lake is located in Isanti County, Minnesota.
When does Florence Lake thaw?
- Florence Lake typically has ice-out around Apr 3. Ice typically forms around Nov 26. The open water season is approximately 237 days.
Are there boat ramps on Florence Lake?
- Florence Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Florence Lake. Public access is listed as yes.
Explore Florence Lake across LakeGrade
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Where this data comes from
165 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
MNPCA165 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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