Silver Lake
McHenry County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Silver Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Public access
- Limited data
Silver Lake in McHenry County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 7 ft visibility. Phosphorus: 12.5 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
Silver Lake is a mesotrophic lake in McHenry County, Illinois. Limited fish-species data available. Public access is available. Compared to the 4 other monitored lakes in McHenry County, Silver Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2020-10-14. Methodology: how these readings are compared.
For a place on the water, look through cabin and lake-house rentals near Silver Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
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. Silver Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Silver 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 Silver Lake
These are the measurements Illinois EPA publishes for Silver Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7 ft. Phosphorus 12.5 µg/L. Chlorophyll-a 4.9 µg/L. TSI 45.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 12.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 4.9µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 45 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Silver Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Silver Lake typically sits around 55°F at the surface in October. Summer average is about 78°F. Usually warmest in Jul (about 81°F) and coldest in Oct (about 55°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (55°F) to its warmest (81°F).
Typical surface water temperature by month, from 122 field readings (2010–2020) via the EPA Water Quality Portal. See the full Silver Lake water temperature breakdown →
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Stays near Silver Lake
Compare lakeside cabins, hotels, and vacation rentals near Silver 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.
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Fishing Silver Lake
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
Designated uses not supporting: Fish consumption, Other.
Source: EPA ATTAINS assessment unit IL_RTW · Official waterbody report
Regulated Pollution Sources Nearby
6 EPA-permitted facilities operate within about 5 miles of Silver Lake under Clean Water Act (NPDES) discharge permits, including 3 classified by the EPA as major dischargers. 4 facilities have a reported Clean Water Act violation in the past three years.
- Crystal Lake Wwtp #3Crystal Lake · 2.9 mi away · NPDES IL0053457MajorRecent violation
- Cary Wwtp, Village OfCary · 2.9 mi away · NPDES IL0020516MajorRecent violation
- Fox River Grove WwtpFox River Grove · 3.8 mi away · NPDES IL0020583MajorRecent violation
- Mathews CompanyCrystal Lake · 4 mi away · NPDES IL0072851Recent violation
- Killarney Water SystemCary · 0.9 mi away · NPDES ILG640285
- Precision Twist Drill CorpCrystal Lake · 2.6 mi away · NPDES IL0074276
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 Silver Lake
Where is Silver Lake?
- Silver 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 Silver Lake?
- Silver Lake in McHenry County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 7 ft visibility. Phosphorus: 12.5 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
Is Silver Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Silver Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Silver Lake?
- Silver Lake typically sits around 55°F at the surface in October, from 122 EPA Water Quality Portal field readings (2010–2020). That is a typical value for the month, not a live reading.
Can I fish at Silver Lake?
- Public access to Silver 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 Silver Lake across LakeQuality
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Where this data comes from
52 measurements from 3 monitoring stations, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX52 samples · 2020
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)