Hay Lake Water Temperature
Hay Lake in Cass County, Minnesota averages about 59°F at the surface in summer — warmest in Aug (~60°F) and coldest in May (~49°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 127 field readings (2011–2024) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Hay Lake warm enough to swim?
Wetsuit territory. Brief exposure is tolerable but prolonged swimming without protection risks hypothermia.
Want more than temperature? Hay Lake scored A on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
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Frequently asked questions
What is the water temperature of Hay Lake?
Hay Lake has a typical summer surface temperature of about 59°F. It is usually warmest in August (around 60°F) and coldest in May (around 49°F). These are typical values by month from 127 EPA Water Quality Portal field readings (2011–2024), not a live reading.
When is Hay Lake warmest?
Surface water at Hay Lake is typically warmest in August, reaching about 60°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 Hay Lake warm enough to swim?
At its typical summer peak of about 59°F, Hay Lake rates as "cold" for swimming. Wetsuit territory. Brief exposure is tolerable but prolonged swimming without protection risks hypothermia.
Where does this Hay 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 — 127 readings from 1 monitoring station between 2011 and 2024. 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.