Horsetail Lake Water Temperature
Horsetail Lake in Cook County, Illinois typically sits around 68°F at the surface in September — warmest in Jul (~84°F) and coldest in Oct (~58°F). That is a typical value for the month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 42 field readings (2010–2022) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Horsetail Lake warm enough to swim?
Very comfortable for swimming. Warm surface water can also favor blue-green algae in nutrient-rich lakes, so check for advisories before you go in.
Want more than temperature? Horsetail Lake water quality: clarity, algae, phosphorus, depth, fish species, and current advisories, all on one page.
Water temperatures at nearby Illinois lakes
Summer average ~80°F
Summer average ~79°F
Summer average ~72°F
Summer average ~78°F
Summer average ~76°F
Summer average ~69°F
Explore water temperatures
Where to stay near Horsetail Lake
Planning a swim or lake trip? Compare cabins, lodges, and vacation rentals near Horsetail Lake — live availability and prices. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Horsetail Lake
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Frequently asked questions
What is the water temperature of Horsetail Lake?
Horsetail Lake typically sits around 68°F at the surface in September, from 42 EPA Water Quality Portal field readings (2010–2022). That is a typical value for the month, not a live reading.
When is Horsetail Lake warmest?
Surface water at Horsetail Lake is typically warmest in July, reaching about 84°F. Lake surface temperature lags air temperature by several weeks, so the warmest water usually arrives in mid-to-late summer even though the hottest air can come earlier.
Is Horsetail Lake warm enough to swim?
At its typical summer peak of about 81°F, Horsetail Lake rates as "warm" for swimming. Very comfortable for swimming. Warm surface water can also favor blue-green algae in nutrient-rich lakes, so check for advisories before you go in.
Where does this Horsetail Lake water temperature data come from?
Every temperature on this page is a typical (climatological) value computed from real surface-water field readings collected by state and federal agencies and published through the EPA Water Quality Portal — 42 readings from 2 monitoring stations between 2010 and 2022. They describe what is typical for each month, not the temperature right now.
About this data
Water temperatures are a climatology — the typical value for each month, averaged from real surface-water field readings collected by state and federal agencies and published through the EPA Water Quality Portal. They tell you what to expect, not the temperature at this moment. Actual conditions vary with recent weather, depth, and time of day.