Horsetail Lake
Cook County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Horsetail Lake. Here is what has been measured.
- Hypereutrophic
- Limited data
Horsetail Lake in Cook County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 2.2 ft visibility. Phosphorus: 45 µg/L. Chlorophyll-a (algae): 39.6 µg/L.
Horsetail Lake is a highly nutrient-loaded hypereutrophic lake in Cook County, Illinois. Compared to the 15 other monitored lakes in Cook County, Horsetail Lake ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-03-24. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Horsetail 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 Horsetail Lake
These are the measurements Illinois EPA publishes for Horsetail Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.2 ft of visibility. Phosphorus 45 µg/L. Chlorophyll-a 39.6 µg/L. TSI 64.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 45µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 39.6µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 64 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Horsetail Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Horsetail Lake typically sits around 58°F at the surface in October. Summer average is about 81°F. Usually warmest in Jul (about 84°F) and coldest in Oct (about 58°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (58°F) to its warmest (84°F).
Typical surface water temperature by month, from 42 field readings (2010–2022) via the EPA Water Quality Portal. See the full Horsetail Lake water temperature breakdown →
Stays via Stay22
Stays near Horsetail Lake
Compare lakeside cabins, hotels, and vacation rentals near Horsetail 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Horsetail Lake are listed below.
Top-rated places to stay near Horsetail Lake
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Illinois’s top lakes →
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Fishing Horsetail Lake
Nearby Lakes in Cook County
Frequently asked questions about Horsetail Lake
Where is Horsetail Lake?
- Horsetail Lake is a lake in Cook County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Horsetail Lake?
- Horsetail Lake in Cook County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 2.2 ft visibility. Phosphorus: 45 µg/L. Chlorophyll-a (algae): 39.6 µg/L.
Is Horsetail Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Horsetail Lake?
- Horsetail Lake typically sits around 58°F at the surface in October, from 42 EPA Water Quality Portal field readings (2010–2022). That is a typical value for the month, not a live reading.
Explore Horsetail Lake across LakeQuality
More lakes in Illinois
Other Lakes in Illinois
Hypereutrophic Lakes in Illinois
Where this data comes from
37 measurements from 3 monitoring stations, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX36 samples · 2020 - USGS Illinois Water Science Center
USGS-IL1 sample · 2022
Analytical methods
- Secchi disk method
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (3)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.