Portage Lake Southwest Basin; Mendon Township Water Temperature
Portage Lake Southwest Basin; Mendon Township in St. Joseph County, Michigan averages about 64°F at the surface in summer — warmest in Jul (~65°F) and coldest in May (~58°F). These are typical values by month, not a live reading.
Typical water temperature by month
Typical surface water temperature by month, from 277 field readings (2016–2019) via the EPA Water Quality Portal. Months with too few readings are left blank.
Is Portage Lake Southwest Basin; Mendon Township warm enough to swim?
Brisk but swimmable for short dips — most people acclimate after the first few minutes.
Want more than temperature? Portage Lake Southwest Basin; Mendon Township scored D on water quality — clarity, algae, phosphorus, depth, fish species, and swimming safety, all on one report card.
Water temperatures at nearby Michigan lakes
Summer average ~62°F
Summer average ~72°F
Summer average ~58°F
Summer average ~77°F
Summer average ~54°F
Summer average ~57°F
Explore water temperatures
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Frequently asked questions
What is the water temperature of Portage Lake Southwest Basin; Mendon Township?
Portage Lake Southwest Basin; Mendon Township has a typical summer surface temperature of about 64°F. It is usually warmest in July (around 65°F) and coldest in May (around 58°F). These are typical values by month from 277 EPA Water Quality Portal field readings (2016–2019), not a live reading.
When is Portage Lake Southwest Basin; Mendon Township warmest?
Surface water at Portage Lake Southwest Basin; Mendon Township is typically warmest in July, reaching about 65°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 Portage Lake Southwest Basin; Mendon Township warm enough to swim?
At its typical summer peak of about 64°F, Portage Lake Southwest Basin; Mendon Township rates as "cool" for swimming. Brisk but swimmable for short dips — most people acclimate after the first few minutes.
Where does this Portage Lake Southwest Basin; Mendon Township 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 — 277 readings from 1 monitoring station between 2016 and 2019. 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.