Tree Lake Water Temperature
Tree Lake in Portage County, Wisconsin averages about 76°F at the surface in summer — warmest in Jul (~79°F) and coldest in Feb (~34°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 62 field readings (2024–2026) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Tree Lake warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Tree Lake scored B on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
Water temperatures at nearby Wisconsin lakes
Summer average ~75°F
Summer average ~73°F
Summer average ~76°F
Summer average ~78°F
Summer average ~77°F
Summer average ~76°F
Explore water temperatures
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Frequently asked questions
What is the water temperature of Tree Lake?
Tree Lake has a typical summer surface temperature of about 76°F. It is usually warmest in July (around 79°F) and coldest in February (around 34°F). These are typical values by month from 62 EPA Water Quality Portal field readings (2024–2026), not a live reading.
When is Tree Lake warmest?
Surface water at Tree Lake is typically warmest in July, reaching about 79°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 Tree Lake warm enough to swim?
At its typical summer peak of about 76°F, Tree Lake rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Tree 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 — 62 readings from 1 monitoring station between 2024 and 2026. 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.