O'Brien Lake Water Temperature
O'Brien Lake in Itasca County, Minnesota typically sits around 63°F at the surface in September — warmest in Aug (~71°F) and coldest in May (~56°F). That is a typical value for the month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 106 field readings (2025–2025) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is O'Brien Lake warm enough to swim?
Brisk but swimmable for short dips — most people acclimate after the first few minutes.
Want more than temperature? O'Brien Lake scored NR 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 ~63°F
Summer average ~55°F
Summer average ~72°F
Summer average ~65°F
Summer average ~68°F
Summer average ~63°F
Explore water temperatures
Where to stay near O'Brien Lake
Planning a swim or lake trip? Compare cabins, lodges, and vacation rentals near O'Brien 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 O'Brien Lake
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Frequently asked questions
What is the water temperature of O'Brien Lake?
O'Brien Lake typically sits around 63°F at the surface in September, from 106 EPA Water Quality Portal field readings (2025–2025). That is a typical value for the month, not a live reading.
When is O'Brien Lake warmest?
Surface water at O'Brien Lake is typically warmest in August, reaching about 71°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 O'Brien Lake warm enough to swim?
At its typical summer peak of about 68°F, O'Brien Lake rates as "cool" for swimming. Brisk but swimmable for short dips — most people acclimate after the first few minutes.
Where does this O'Brien 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 — 106 readings from 2 monitoring stations between 2025 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.