Bullfrog Lake Water Temperature
Bullfrog Lake in Cook County, Illinois averages about 78°F at the surface in summer — warmest in Aug (~81°F) and coldest in Oct (~60°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 29 field readings (2010–2023) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Bullfrog Lake warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Bullfrog 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 ~76°F
Summer average ~72°F
Summer average ~80°F
Summer average ~69°F
Summer average ~77°F
Summer average ~75°F
Explore water temperatures
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Frequently asked questions
What is the water temperature of Bullfrog Lake?
Bullfrog Lake has a typical summer surface temperature of about 78°F. It is usually warmest in August (around 81°F) and coldest in October (around 60°F). These are typical values by month from 29 EPA Water Quality Portal field readings (2010–2023), not a live reading.
When is Bullfrog Lake warmest?
Surface water at Bullfrog Lake is typically warmest in August, 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 Bullfrog Lake warm enough to swim?
At its typical summer peak of about 78°F, Bullfrog Lake rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Bullfrog 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 — 29 readings from 2 monitoring stations between 2010 and 2023. 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.