Big Rock Lake Water Temperature
Big Rock Lake in Kane County, Illinois averages about 57°F at the surface in summer — warmest in Aug (~58°F) and coldest in May (~51°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 231 field readings (2022–2022) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Big Rock Lake warm enough to swim?
Wetsuit territory. Brief exposure is tolerable but prolonged swimming without protection risks hypothermia.
Want more than temperature? Big Rock 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 ~69°F
Summer average ~73°F
Summer average ~69°F
Summer average ~78°F
Summer average ~74°F
Summer average ~77°F
Explore water temperatures
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Frequently asked questions
What is the water temperature of Big Rock Lake?
Big Rock Lake has a typical summer surface temperature of about 57°F. It is usually warmest in August (around 58°F) and coldest in May (around 51°F). These are typical values by month from 231 EPA Water Quality Portal field readings (2022–2022), not a live reading.
When is Big Rock Lake warmest?
Surface water at Big Rock Lake is typically warmest in August, reaching about 58°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 Big Rock Lake warm enough to swim?
At its typical summer peak of about 57°F, Big Rock Lake rates as "cold" for swimming. Wetsuit territory. Brief exposure is tolerable but prolonged swimming without protection risks hypothermia.
Where does this Big Rock 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 — 231 readings from 2 monitoring stations between 2022 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.