Silver Lake is a mesotrophic lake in McHenry County, Illinois. Water quality is graded B based on 1 sampling years through 2020. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 4 other monitored lakes in McHenry County, Silver Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2020-07-18. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 10 ft. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Silver Lake
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Fishing Silver Lake
Recreation & Access
Water Temperature
Silver 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 71 field readings (2010–2020) via the EPA Water Quality Portal.
Location
County Ranking
Ranked #2 of 5 lakes in McHenry County
Nearby Lakes in McHenry County
Explore Silver 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
Moderate nutrients, good water quality
Illinois's cleanest and most-polluted lakes, ranked
More Illinois Lake Rankings
Other Grade B Lakes in Illinois
Mesotrophic Lakes in Illinois
More records, surveys & data sources
Reservoir Info (USACE NID)
Silver Lake is a man-made reservoir impounded by the Silver Lake Dam (completed 1929), built primarily for recreation on the TRIB FOX RIVER; earth-type dam, 23 ft tall and 170 ft long.
- Normal storage
- 364 ac-ft
- Max storage
- 580 ac-ft
- Hazard class
- Low
- Owner
- VILLAGE OF OAKWOOD HILLS
Source: USACE National Inventory of Dams, NID ID IL00584 · Operator website
EPA Impairment Status
Silver Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IL_RTW · Official waterbody report · Matched by proximity (0.1 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Silver 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.
- Northern Moraine Ww Reclamation Dist WwtpIsland Lake · 2.7 mi away · NPDES IL0031933MajorRecent violation
- Illinois American Water CompanyCrystal Lake · 2.7 mi away · NPDES IL0038202Recent violation
- Snap-On ToolsCrystal Lake · 0.3 mi away · NPDES IL0065480
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2020-07-18
Monitoring stations: 1