Petite Lake is a productive, nutrient-rich eutrophic lake in Lake County, Illinois. Water quality is graded D based on 2 sampling years through 2022. Compared to the 15 other monitored lakes in Lake County, Petite Lake ranks #13 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2022-10-26. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 2.5 ft of visibility. Phosphorus level: 36 µg/L. Trophic State Index: 60.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | F |
| Phosphorus | 36 µg/L | C |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Petite Lake
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Fishing Petite Lake
Water Temperature
Petite Lake averages about 78°F at the surface in summer, usually warmest in Jul (about 81°F) and coldest in Oct (about 57°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 113 field readings (2012–2022) via the EPA Water Quality Portal. See the full Petite Lake water temperature breakdown →
Location
County Ranking
Ranked #13 of 16 lakes in Lake County
Cleaner Lakes Within 30 Miles
Petite Lake holds Grade D. 2 nearby lakes hold higher grades.
- BCatherine LakeLake County · 3.8 mi · Two grade letters higher (D → B)
- CChannel LakeLake County · 3.5 mi · Higher grade (D → C)
Nearby Lakes in Lake County
Explore Petite Lake across LakeGrade
Species activity outlook by water temperature and season
Top lakes and where to stay in the Chain O'Lakes area
Where to stay at Illinois's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Illinois's cleanest and most-polluted lakes, ranked
More Illinois Lake Rankings
Other Grade D Lakes in Illinois
Eutrophic Lakes in Illinois
More records, surveys & data sources
EPA Impairment Status
Petite Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_VTW · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-10-26
Monitoring stations: 1