Long Lake Water Temperature
Long Lake in Sauk County, Wisconsin averages about 75°F at the surface in summer — warmest in Jun (~79°F) and coldest in Oct (~50°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 34 field readings (2024–2025) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Long Lake warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Long Lake scored C 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 ~76°F
Summer average ~78°F
Summer average ~67°F
Summer average ~76°F
Summer average ~76°F
Summer average ~76°F
Explore water temperatures
Where to stay near Long Lake
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Frequently asked questions
What is the water temperature of Long Lake?
Long Lake has a typical summer surface temperature of about 75°F. It is usually warmest in June (around 79°F) and coldest in October (around 50°F). These are typical values by month from 34 EPA Water Quality Portal field readings (2024–2025), not a live reading.
When is Long Lake warmest?
Surface water at Long Lake is typically warmest in June, 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 Long Lake warm enough to swim?
At its typical summer peak of about 75°F, Long Lake rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Long 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 — 34 readings from 1 monitoring station between 2024 and 2025. 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.