O'Reilly Lake Water Temperature
O'Reilly Lake in Itasca County, Minnesota typically sits around 67°F at the surface in September — warmest in Jul (~73°F) and coldest in Oct (~58°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 45 field readings (2022–2025) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is O'Reilly Lake warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? O'Reilly 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 ~75°F
Summer average ~72°F
Summer average ~72°F
Summer average ~67°F
Summer average ~65°F
Summer average ~63°F
Explore water temperatures
Where to stay near O'Reilly Lake
Planning a swim or lake trip? Compare cabins, lodges, and vacation rentals near O'Reilly 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'Reilly Lake
Prices for Sep 4–6, 4 adults. Change dates on the map below.
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Frequently asked questions
What is the water temperature of O'Reilly Lake?
O'Reilly Lake typically sits around 67°F at the surface in September, from 45 EPA Water Quality Portal field readings (2022–2025). That is a typical value for the month, not a live reading.
When is O'Reilly Lake warmest?
Surface water at O'Reilly 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 O'Reilly Lake warm enough to swim?
At its typical summer peak of about 72°F, O'Reilly Lake rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this O'Reilly 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 — 45 readings from 1 monitoring station between 2022 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.