Blackwater Lake Water Temperature
Blackwater Lake in Cass County, Minnesota averages about 68°F at the surface in summer — warmest in Aug (~72°F) and coldest in Jul (~62°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 37 field readings (2016–2023) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Blackwater Lake warm enough to swim?
Brisk but swimmable for short dips — most people acclimate after the first few minutes.
Want more than temperature? Blackwater Lake scored A 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 Blackwater Lake?
Blackwater Lake has a typical summer surface temperature of about 68°F. It is usually warmest in August (around 72°F) and coldest in July (around 62°F). These are typical values by month from 37 EPA Water Quality Portal field readings (2016–2023), not a live reading.
When is Blackwater Lake warmest?
Surface water at Blackwater Lake is typically warmest in August, reaching about 72°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 Blackwater Lake warm enough to swim?
At its typical summer peak of about 68°F, Blackwater Lake rates as "cool" for swimming. Brisk but swimmable for short dips — most people acclimate after the first few minutes.
Where does this Blackwater 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 — 37 readings from 1 monitoring station between 2016 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.