Petite Lake
Lake County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Petite Lake. Here is what has been measured.
- Impaired · Mercury
- 34 ft max depth
- Limited data
Petite Lake in Lake County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 70 µg/L. Chlorophyll-a (algae): 59 µg/L.
Petite Lake is a lake in Lake County, Illinois with an estimated average depth of about 34 feet.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-26. Methodology: how these readings are compared.
If you are planning to stay, you can search lake houses and cabins around Petite Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Petite Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), pCBs. Check local advisories before you swim.
Whether Petite Lake is safe to swim in today is a call for the Illinois Environmental Protection Agency and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Petite Lake
These are the measurements Illinois EPA publishes for Petite Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.5 ft of visibility. Phosphorus 70 µg/L. Chlorophyll-a 59 µg/L. TSI 67.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 70µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 59µg/L | Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water. |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 67 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Petite Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Petite Lake typically sits around 57°F at the surface in October. Summer average is about 78°F. Usually warmest in Jul (about 81°F) and coldest in Oct (about 57°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (57°F) to its warmest (81°F).
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 →
Lake Details
Max depth
~34 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Petite Lake.
Lake Size & Watershed
Watershed (drainage) area
3 sq mi
HydroLAKES / HydroSHEDS
Surface area
166 acres
HydroLAKES / HydroSHEDS
Shoreline
2.7 mi
HydroLAKES / HydroSHEDS
Elevation
735 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
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Stays near Petite Lake
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Top-rated places to stay near Petite Lake
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Fishing Petite Lake
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
Designated uses not supporting: Fish consumption, Other.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_VTW · Official waterbody report
Nearby Lakes in Lake County
Frequently asked questions about Petite Lake
Where is Petite Lake?
- Petite Lake is a lake in Lake County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Petite Lake?
- Petite Lake in Lake County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 70 µg/L. Chlorophyll-a (algae): 59 µg/L.
Is Petite Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Petite Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), pCBs. Check local advisories before you swim.
What is the water temperature of Petite Lake?
- Petite Lake typically sits around 57°F at the surface in October, from 113 EPA Water Quality Portal field readings (2012–2022). That is a typical value for the month, not a live reading.
How deep is Petite Lake?
- No published bathymetric survey covers Petite Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 34 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
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Where this data comes from
13 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX13 samples · 2022
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)