Jamestown Reservoir Water Temperature
Jamestown Reservoir in Stutsman County, North Dakota averages about 70°F at the surface in summer — warmest in Jul (~74°F) and coldest in Oct (~54°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 369 field readings (2012–2025) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Jamestown Reservoir warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Jamestown Reservoir scored D on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
Water temperatures at nearby North Dakota lakes
Summer average ~60°F
Summer average ~60°F
Summer average ~61°F
Summer average ~63°F
Summer average ~63°F
Summer average ~63°F
Explore water temperatures
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Frequently asked questions
What is the water temperature of Jamestown Reservoir?
Jamestown Reservoir has a typical summer surface temperature of about 70°F. It is usually warmest in July (around 74°F) and coldest in October (around 54°F). These are typical values by month from 369 EPA Water Quality Portal field readings (2012–2025), not a live reading.
When is Jamestown Reservoir warmest?
Surface water at Jamestown Reservoir is typically warmest in July, reaching about 74°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 Jamestown Reservoir warm enough to swim?
At its typical summer peak of about 70°F, Jamestown Reservoir rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Jamestown Reservoir 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 — 369 readings from 2 monitoring stations between 2012 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.