Grass Lake Water Temperature
Grass Lake in Hennepin County, Minnesota typically sits around 58°F at the surface in October — warmest in Jul (~77°F) and coldest in Apr (~44°F). That is a typical value for the month, not a live reading.
Typical water temperature by month
Column height runs from this lake’s coldest month (44°F) to its warmest (77°F).
Typical surface water temperature by month, from 18 field readings (2010–2024) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Grass Lake warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Grass Lake water quality: clarity, algae, phosphorus, depth, fish species, and current advisories, all on one page.
Water temperatures at nearby Minnesota lakes
Summer average ~55°F
Summer average ~80°F
Summer average ~73°F
Summer average ~55°F
Summer average ~71°F
Summer average ~62°F
Explore water temperatures
Where to stay near Grass Lake
Planning a swim or lake trip? Compare cabins, lodges, and vacation rentals near Grass Lake — live availability and prices. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Grass Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Frequently asked questions
What is the water temperature of Grass Lake?
Grass Lake typically sits around 58°F at the surface in October, from 18 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
When is Grass Lake warmest?
Surface water at Grass Lake 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 Grass Lake warm enough to swim?
At its typical summer peak of about 72°F, Grass Lake rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Grass 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 — 18 readings from 1 monitoring station between 2010 and 2024. 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.