Tecumseh Lake Water Temperature
Tecumseh Lake in Hardin County, Illinois averages about 80°F at the surface in summer — warmest in Jul (~82°F) and coldest in Apr (~60°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 164 field readings (2010–2020) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Tecumseh 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? Tecumseh Lake scored B 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 ~76°F
Summer average ~75°F
Summer average ~77°F
Summer average ~83°F
Summer average ~73°F
Explore water temperatures
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Frequently asked questions
What is the water temperature of Tecumseh Lake?
Tecumseh Lake has a typical summer surface temperature of about 80°F. It is usually warmest in July (around 82°F) and coldest in April (around 60°F). These are typical values by month from 164 EPA Water Quality Portal field readings (2010–2020), not a live reading.
When is Tecumseh Lake warmest?
Surface water at Tecumseh Lake is typically warmest in July, reaching about 82°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 Tecumseh Lake warm enough to swim?
At its typical summer peak of about 80°F, Tecumseh 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 Tecumseh 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 — 164 readings from 4 monitoring stations between 2010 and 2020. 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.