Catherine Lake
Lake County, IllinoisView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
↑ up from B at the last regrade
- Mesotrophic
- Impaired · Mercury
- #2 of 19 in the county
- Public access
- Limited data
Catherine Lake in Lake County, Illinois has a water quality grade of A (Excellent). Water clarity: 7.4 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
- Clarity
- 7.4 ft
- Typical in August
- 69°F
- Type
- Mesotrophic
- Phosphorus
- 30 µg/L
- Chlorophyll-a
- 4.9 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
Stays via Stay22
Stays near Catherine Lake
Compare lakeside cabins, hotels, and vacation rentals near Catherine 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 Catherine Lake
Prices for Sep 11–13, 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 trip? Cabins and lodging at Catherine Lake → · more Illinois lake trips
Watch Catherine Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Catherine Lake is a mesotrophic lake in Lake County, Illinois. Water quality is graded A based on 2 sampling years through 2022. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 18 other monitored lakes in Lake County, Catherine Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-17. Grade methodology: LakeQuality methodology.
What Catherine Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch3 documented ramps
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The A is nutrients and algae, not a swimming clearance. Catherine Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), pCBs. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Moderate clarity, visible to about 7.4 ft. Phosphorus 30 µg/L. Chlorophyll-a 4.9 µg/L. TSI 49. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.4 ft | Not graded |
| Phosphorus | 30 µg/L | Good |
| Chlorophyll-a (Algae) | 4.9 µg/L | Good |
| Trophic State Index (TSI) | 49 | Mesotrophic |
Moderate nutrients, good water quality
Water Temperature
Catherine Lake typically sits around 69°F at the surface in August. Summer average is about 71°F. Usually warmest in Jul (about 75°F) and coldest in May (about 56°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 443 field readings (2012–2022) via the EPA Water Quality Portal. See the full Catherine Lake water temperature breakdown →
Recreation & Access
- Fox Chain O'LakesPublic
- Lake Marie - Sequoit HarborPublic
- a marinaSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Catherine Lake
Water Quality Trend: ↓ Declining
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -1.639 m/yr | 7 |
| Phosphorus | ↓ Declining | +7.15 µg/L/yr | 3 |
EPA Impairment Status
Catherine Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RTD · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Catherine Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- Salem Utility District No 2Salem · 1.9 mi away · NPDES WI0031496MajorRecent 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.
County Ranking
Ranked #2 of 19 lakes in Lake County
Nearby Lakes in Lake County
Frequently asked questions about Catherine Lake
Where is Catherine Lake?
- Catherine Lake is a lake in Lake County, Illinois. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Catherine Lake?
- Catherine Lake in Lake County, Illinois has a water quality grade of A (Excellent). Water clarity: 7.4 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
Is Catherine Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Catherine Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), pCBs. Check local advisories before you swim.
What is the water temperature of Catherine Lake?
- Catherine Lake typically sits around 69°F at the surface in August, from 443 EPA Water Quality Portal field readings (2012–2022). That is a typical value for the month, not a live reading.
Are there boat ramps on Catherine Lake?
- Catherine Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Fox Chain O'Lakes, Lake Marie - Sequoit Harbor, a marina. Public access is listed as yes.
Explore Catherine 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 grade
Moderate nutrients, good water quality
Illinois's cleanest and most-polluted lakes, ranked
More Illinois Lake Rankings
Other Grade A Lakes in Illinois
Mesotrophic Lakes in Illinois
Where this data comes from
22 measurements from 2 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX22 samples · 2022
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (2)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Named boat-access points from the USGS National Boat Ramps inventory