Lake Mallalieu Water Temperature
Lake Mallalieu in St. Croix County, Wisconsin averages about 74°F at the surface in summer — warmest in Jul (~77°F) and coldest in Mar (~48°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 30 field readings (2024–2025) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Lake Mallalieu warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Lake Mallalieu scored D on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
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Frequently asked questions
What is the water temperature of Lake Mallalieu?
Lake Mallalieu has a typical summer surface temperature of about 74°F. It is usually warmest in July (around 77°F) and coldest in March (around 48°F). These are typical values by month from 30 EPA Water Quality Portal field readings (2024–2025), not a live reading.
When is Lake Mallalieu warmest?
Surface water at Lake Mallalieu is typically warmest in July, reaching about 77°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 Mallalieu warm enough to swim?
At its typical summer peak of about 74°F, Lake Mallalieu rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Lake Mallalieu 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 — 30 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.