Deep Portage Lake Water Temperature
Deep Portage Lake in Cass County, Minnesota averages about 66°F at the surface in summer — warmest in Jul (~73°F) and coldest in Aug (~53°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 84 field readings (2011–2025) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Deep Portage Lake warm enough to swim?
Brisk but swimmable for short dips — most people acclimate after the first few minutes.
Want more than temperature? Deep Portage Lake scored A on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
Water temperatures at nearby Minnesota lakes
Summer average ~74°F
Summer average ~73°F
Summer average ~64°F
Summer average ~66°F
Summer average ~72°F
Summer average ~67°F
Explore water temperatures
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Frequently asked questions
What is the water temperature of Deep Portage Lake?
Deep Portage Lake has a typical summer surface temperature of about 66°F. It is usually warmest in July (around 73°F) and coldest in August (around 53°F). These are typical values by month from 84 EPA Water Quality Portal field readings (2011–2025), not a live reading.
When is Deep Portage Lake warmest?
Surface water at Deep Portage Lake is typically warmest in July, reaching about 73°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 Deep Portage Lake warm enough to swim?
At its typical summer peak of about 66°F, Deep Portage Lake rates as "cool" for swimming. Brisk but swimmable for short dips — most people acclimate after the first few minutes.
Where does this Deep Portage 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 — 84 readings from 2 monitoring stations between 2011 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.