Lily Lake
McHenry County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Lily Lake. Here is what has been measured.
- Eutrophic
- Impaired · Noxious aquatic plants
- 36 ft max depth
- Public access
- Limited data
Lily Lake in McHenry County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 19 µg/L. Chlorophyll-a (algae): 25.4 µg/L.
Lily Lake is a productive, nutrient-rich eutrophic lake in McHenry County, Illinois with an estimated average depth of about 36 feet. Limited fish-species data available. Public access is available. Compared to the 4 other monitored lakes in McHenry County, Lily Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2021-10-12. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Lily Lake is listed impaired under Clean Water Act §303(d) (IR 5) for noxious aquatic plants, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Lily 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 Lily Lake
These are the measurements Illinois EPA publishes for Lily 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 3.3 ft of visibility. Phosphorus 19 µg/L. Chlorophyll-a 25.4 µg/L. TSI 56.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 19µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 25.4µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 56 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lily Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lily Lake typically sits around 58°F at the surface in October. Summer average is about 73°F. Usually warmest in Aug (about 76°F) and coldest in Oct (about 58°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (58°F) to its warmest (76°F).
Typical surface water temperature by month, from 160 field readings (2012–2021) via the EPA Water Quality Portal. See the full Lily Lake water temperature breakdown →
Lake Details
Max depth
~36 ft est.
Public access
Yes
Listed by Illinois EPA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Lily Lake.
Lake Size & Watershed
Watershed (drainage) area
0 sq mi
HydroLAKES / HydroSHEDS
Surface area
94 acres
HydroLAKES / HydroSHEDS
Shoreline
1.9 mi
HydroLAKES / HydroSHEDS
Elevation
748 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.
Stays via Stay22
Stays near Lily Lake
Compare lakeside cabins, hotels, and vacation rentals near Lily Lake in McHenry County, Illinois — 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Lily Lake are listed below.
Top-rated places to stay near Lily Lake
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Illinois’s top lakes →
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Fishing Lily Lake
EPA Impairment Status
Lily 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: Other.
Source: EPA ATTAINS assessment unit IL_RTZJ · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Lily Lake under Clean Water Act (NPDES) discharge permits, including 2 classified by the EPA as major dischargers. 1 facility has a reported Clean Water Act violation in the past three years.
- Mchenry - South WwtpMchenry · 2.6 mi away · NPDES IL0066257MajorRecent violation
- City Of Mchenry - Central WwtpMchenry · 3 mi away · NPDES IL0021067Major
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.
Nearby Lakes in McHenry County
Frequently asked questions about Lily Lake
Where is Lily Lake?
- Lily Lake is a lake in McHenry County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Lily Lake?
- Lily Lake in McHenry County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 19 µg/L. Chlorophyll-a (algae): 25.4 µg/L.
Is Lily Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lily Lake is listed impaired under Clean Water Act §303(d) (IR 5) for noxious aquatic plants, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Lily Lake?
- Lily Lake typically sits around 58°F at the surface in October, from 160 EPA Water Quality Portal field readings (2012–2021). That is a typical value for the month, not a live reading.
How deep is Lily Lake?
- No published bathymetric survey covers Lily Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 36 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Can I fish at Lily Lake?
- Public access to Lily Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Illinois's fish and wildlife agency, so check its current regulations before you go.
Explore Lily Lake across LakeQuality
Species activity outlook by water temperature and season
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Where this data comes from
52 measurements from 3 monitoring stations, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX52 samples · 2021
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (3)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)