Lake Monona Water Temperature
Lake Monona in Dane County, Wisconsin averages about 77°F at the surface in summer — warmest in Jul (~78°F) and coldest in Jun (~76°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 18 field readings (2024–2025) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Lake Monona warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
A live gauge on Lake Monona last read 78°F. See the full Lake Monona report card for current conditions and the A–F water-quality grade.
Want more than temperature? Lake Monona scored D on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
Water temperatures at nearby Wisconsin lakes
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Frequently asked questions
What is the water temperature of Lake Monona?
Lake Monona has a typical summer surface temperature of about 77°F. It is usually warmest in July (around 78°F) and coldest in June (around 76°F). These are typical values by month from 18 EPA Water Quality Portal field readings (2024–2025), not a live reading.
When is Lake Monona warmest?
Surface water at Lake Monona is typically warmest in July, reaching about 78°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 Monona warm enough to swim?
At its typical summer peak of about 77°F, Lake Monona rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Lake Monona 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 — 18 readings from 2 monitoring stations 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.