Southwestern Ontario County Lake Quality
Ontario, 1 lakes, average grade A (Excellent)
Only 1 lakes in Southwestern Ontario 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. The county's average grade is A — among the cleanest in Ontario. 1 lakes pull an A on their own, and almost none fall into the D or F brackets.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Huron Lake (A); the most-stressed is Huron Lake (A).
Quick Answers for Southwestern Ontario County
Planning a trip? Check special fishing regulations for Huron Lake — or check the official Ontario fishing regulations.
All Lakes in Southwestern Ontario County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Huron Lake | A | 16.4 ft | 6.6 µg/L |
Other Counties in Ontario
See how Southwestern Ontario County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 38 states.
Where to stay near Southwestern Ontario County
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Source: EPA National Aquatic Resource Surveys, 2026.