Summit Lake Water Temperature
Summit Lake in Union County, Iowa averages about 78°F at the surface in summer — warmest in Jul (~80°F) and coldest in Sep (~70°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 26 field readings (2010–2023) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Summit Lake warm enough to swim?
Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Want more than temperature? Summit Lake scored F on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
Water temperatures at nearby Iowa lakes
Summer average ~78°F
Summer average ~78°F
Summer average ~77°F
Summer average ~78°F
Summer average ~77°F
Summer average ~79°F
Explore water temperatures
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Frequently asked questions
What is the water temperature of Summit Lake?
Summit Lake has a typical summer surface temperature of about 78°F. It is usually warmest in July (around 80°F) and coldest in September (around 70°F). These are typical values by month from 26 EPA Water Quality Portal field readings (2010–2023), not a live reading.
When is Summit Lake warmest?
Surface water at Summit Lake is typically warmest in July, reaching about 80°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 Summit Lake warm enough to swim?
At its typical summer peak of about 78°F, Summit Lake rates as "comfortable" for swimming. Pleasant for swimming — the range most people find enjoyable without a wetsuit.
Where does this Summit 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 — 26 readings from 2 monitoring stations between 2010 and 2023. 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.