Flatfoot Lake Water Temperature
Flatfoot Lake in Cook County, Illinois typically sits around 78°F at the surface in September — warmest in Jul (~81°F) and coldest in Oct (~60°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 58 field readings (2016–2022) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Flatfoot Lake warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Flatfoot Lake scored D on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
Water temperatures at nearby Illinois lakes
Summer average ~78°F
Summer average ~78°F
Summer average ~69°F
Summer average ~78°F
Summer average ~78°F
Summer average ~76°F
Explore water temperatures
Where to stay near Flatfoot Lake
Planning a swim or lake trip? Compare cabins, lodges, and vacation rentals near Flatfoot 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 Flatfoot Lake
Prices for Sep 4–6, 4 adults. Change dates on the map below.
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Frequently asked questions
What is the water temperature of Flatfoot Lake?
Flatfoot Lake typically sits around 78°F at the surface in September, from 58 EPA Water Quality Portal field readings (2016–2022). That is a typical value for the month, not a live reading.
When is Flatfoot Lake warmest?
Surface water at Flatfoot Lake is typically warmest in July, reaching about 81°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 Flatfoot Lake warm enough to swim?
At its typical summer peak of about 78°F, Flatfoot Lake rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Flatfoot 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 — 58 readings from 2 monitoring stations between 2016 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.