McHenry County Lake Quality
Illinois, 5 lakes, average grade C (Fair)
Only 5 lakes in McHenry County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. McHenry County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Silver Lake (B) is the cleanest in the county.
Quick Answers for McHenry County
Planning a trip? Check special fishing regulations for Silver Lake — or check the official Illinois fishing regulations.
All Lakes in McHenry County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Silver Lake | B | 7 ft | 11 µg/L |
| 2 | Silver Lake | B | 10 ft | - |
| 3 | Lily Lake | B | 3.3 ft | 16 µg/L |
| 4 | Woods Creek Lake | C | 3.9 ft | 45.5 µg/L |
| 5 | Pistakee Lake | D | 2.7 ft | 63 µg/L |
Other Counties in Illinois
See how McHenry County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 15 states.
Where to stay near McHenry County
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Source: EPA National Aquatic Resource Surveys, 2026.