Napoleon Lake Water Temperature
Napoleon Lake in Itasca County, Minnesota averages about 70°F at the surface in summer — warmest in Jul (~73°F) and coldest in May (~54°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 88 field readings (2018–2025) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Napoleon Lake warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Napoleon 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
Explore water temperatures
Where to stay near Napoleon Lake
Planning a swim or lake trip? Compare cabins, lodges, and vacation rentals near Napoleon Lake — live availability and prices.
Top-rated places to stay near Napoleon Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Napoleon Lake?
Get lake water-quality report cards plus the best cabin & lodging deals near Napoleon Lake — straight to your inbox. No spam, unsubscribe anytime.
Frequently asked questions
What is the water temperature of Napoleon Lake?
Napoleon Lake has a typical summer surface temperature of about 70°F. It is usually warmest in July (around 73°F) and coldest in May (around 54°F). These are typical values by month from 88 EPA Water Quality Portal field readings (2018–2025), not a live reading.
When is Napoleon Lake warmest?
Surface water at Napoleon 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 Napoleon Lake warm enough to swim?
At its typical summer peak of about 70°F, Napoleon Lake rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Napoleon 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 — 88 readings from 2 monitoring stations between 2018 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.