Bull Frog Lake is a productive, nutrient-rich eutrophic lake in Cook County, Illinois. Water quality is graded F based on 1 sampling years through 2022. Compared to the 67 other monitored lakes in Cook County, Bull Frog Lake ranks #46 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2022-03-21. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 3 ft of visibility. Trophic State Index: 61.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 61 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Bull Frog Lake
Compare lakeside cabins, hotels, and vacation rentals near Bull Frog Lake in Cook 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 Bull Frog Lake
Water Temperature
Bull Frog Lake averages about 76°F at the surface in summer, usually warmest in Aug (about 79°F) and coldest in Oct (about 60°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 45 field readings (2010–2022) via the EPA Water Quality Portal. See the full Bull Frog Lake water temperature breakdown →
Location
County Ranking
Ranked #46 of 68 lakes in Cook County
Cleaner Lakes Within 30 Miles
Bull Frog Lake holds Grade F. 3 nearby lakes hold higher grades.
Nearby Lakes in Cook County
Explore Bull Frog Lake across LakeGrade
More Illinois Lake Rankings
Other Grade F Lakes in Illinois
Eutrophic Lakes in Illinois
More records, surveys & data sources
Reservoir Info (USACE NID)
Bull Frog Lake is a man-made reservoir impounded by the Bullfrog Lake Dam (completed 1958), built primarily for recreation on the TRIB DES PLAINES RIVER; earth-type dam, 17 ft tall and 700 ft long.
- Normal storage
- 77 ac-ft
- Max storage
- 144 ac-ft
- Hazard class
- Significant
- Owner
- FOREST PRESERVE DISTRICT OF COOK COUNTY
Source: USACE National Inventory of Dams, NID ID IL00869 · Operator website
EPA Impairment Status
Bull Frog 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_RHZF · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Bull Frog Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Rowell Chemical CorporationWillow Springs · 0.7 mi away · NPDES IL0066613Recent violation
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)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-03-21
Monitoring stations: 1