Forest Lake
Lake County, Illinois40 acresView mapDirections
No nutrient or algae sampling on record from Illinois EPA for this lake.
- Impaired · Nutrients (phosphorus, nitrogen)
- 9 ft max depth
Forest Lake in Lake County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 9 ft. Surface area: 40 acres.
Forest Lake is a 40-acre lake in Lake County, Illinois with a maximum depth of 9 feet (5-foot average).
Source: EPA Water Quality Portal sampling records, Illinois EPA. Methodology: how these readings are compared.
Swimming conditions
No readingNot rated
Nutrient and algae readings are not a swimming clearance. Forest Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen), turbidity. Check local advisories before you swim.
Whether Forest 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 Forest Lake
These are the measurements Illinois EPA publishes for Forest Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. TSI undefined.
Ask about Forest Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
9 ft
Average depth
4.5 ft
Surface area
40 acres
Shoreline
1.6 mi
Stays via Stay22
Stays near Forest Lake
Compare lakeside cabins, hotels, and vacation rentals near Forest Lake in Lake 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.
Top-rated places to stay near Forest Lake
Prices for Oct 16–18, 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 →
Follow Forest Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Forest Lake
EPA Impairment Status
Forest 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.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RGZG · Official waterbody report
Nearby Lakes in Lake County
Frequently asked questions about Forest Lake
Where is Forest Lake?
- Forest Lake is a lake in Lake County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Forest Lake?
- Forest Lake in Lake County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 9 ft. Surface area: 40 acres.
Is Forest Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Forest Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen), turbidity. Check local advisories before you swim.
How deep is Forest Lake?
- Forest Lake has a maximum depth of 9 feet and an average depth of 4.5 feet. The lake covers 40 acres.
Explore Forest Lake across LakeQuality
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 readings
Illinois's cleanest lakes, ranked on agency measurements
More lakes in Illinois
Other Lakes in Illinois
Where this data comes from
Measurements for Forest Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database