Lake of Egypt Water Temperature
Lake of Egypt in Williamson County, Illinois averages about 82°F at the surface in summer — warmest in Aug (~85°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 217 field readings (2010–2020) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Lake of Egypt 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? Lake of Egypt scored C 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 ~73°F
Summer average ~77°F
Summer average ~75°F
Summer average ~83°F
Summer average ~78°F
Summer average ~68°F
Explore water temperatures
Where to stay near Lake of Egypt
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Frequently asked questions
What is the water temperature of Lake of Egypt?
Lake of Egypt has a typical summer surface temperature of about 82°F. It is usually warmest in August (around 85°F) and coldest in April (around 60°F). These are typical values by month from 217 EPA Water Quality Portal field readings (2010–2020), not a live reading.
When is Lake of Egypt warmest?
Surface water at Lake of Egypt is typically warmest in August, reaching about 85°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 Lake of Egypt warm enough to swim?
At its typical summer peak of about 82°F, Lake of Egypt 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 Lake of Egypt 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 — 217 readings from 1 monitoring station 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.