Best Month to Swim, by State — Typical Lake Temperatures

8 U.S. states have enough temperature sampling on their low-nutrient lakes to name a typical swim month. 5 of them land on July. These are long-run typical temperatures for each month, so treat them as a guide to when the season usually arrives rather than a reading for today.

Driving the news

8 of the 36 U.S. states we cover have enough monthly temperature sampling on low-nutrient lakes to name a typical month. The rest are left blank rather than estimated.
Minnesota’s most comfortable month on low-nutrient lakes is July, typically about 75°F, across 385 lakes.
Florida lands on May (about 81°F) rather than midsummer, because by July and August the surface often runs hotter than the 68–82°F band most swimmers find pleasant.

What “typical” means here

Every number in this report is a typical value for that month, built from surface temperature readings that state and federal crews collected while sampling lakes over many years. It answers a planning question — when does swimming season usually start and end where I live — rather than a same-day one. Only a few dozen U.S. lakes carry a live temperature gauge; where one exists, its current reading appears on that lake’s page with a timestamp.

The comfort band used here is 68–82°F. If any month’s typical temperature across a state’s lowest-nutrient lakes falls inside that range, that month is the pick. If every sampled month is colder or hotter than the band, the warmest month wins and the table still shows its temperature, so you can see how far off it is. Month-by-month charts for individual lakes are on each lake’s best times to visit page.

Best typical swim month, by state

States are listed alphabetically, starting with Florida — this is not a ranking. The temperature column is the middle value across that state’s low-nutrient lakes for the month named, and the last column shows how many lakes went into it.

State	Typical month	Median °F	Favourable-class lakes with temps
Florida	May	81	316
Iowa	July	81	17
Michigan	August	67	53
Minnesota	July	75	385
Missouri	August	82	38
North Dakota	July	72	8
New York	July	73	3
Wisconsin	July	77	238

28 of the U.S. states we cover do not yet have three low-nutrient lakes with temperature readings across enough months to include. This table covers the U.S. only; 41 jurisdictions are graded in total, including Canadian provinces and European bathing waters that run on a different season.

What the table cannot tell you

A typical July of 75°F across Minnesota’s cleanest lakes does not mean a particular lake is 75°F on July 15 of this year, that the beach is open, or that cyanobacteria are absent. Water temperature is comfort; it says nothing about bacteria or algae. Before a swim, look at the lake’s own page for its grade, its month-by-month temperatures, and any live gauge, then check your state’s beach and algae advisories — those are the only source for a same-day answer.

For nutrient-first swim shortlists, see Best Lakes for Swimming and Summer 2026 Cleanest Swim Lakes. For how bacteria advisories actually work, see Is It Safe to Swim?.

Frequently Asked Questions

It depends on the state. Among the lowest-nutrient Minnesota lakes with enough monthly samples, the typical most-comfortable month is July at about 75°F. Florida’s lowest-nutrient set peaks earlier because midsummer surface readings often run hotter than a 68–82°F comfort band. These are multi-year typical values, not a forecast for this week.

No. These are typical surface temperatures by month, averaged from EPA Water Quality Portal field samples collected over many years. A cold spring or a heat wave will move any given year off the typical value. Where a lake has a live USGS gauge, the current reading is on that lake’s own page with the date it was taken.

A state appears only when at least three lakes with low nutrient readings there have monthly temperature readings in at least three months — enough to see a seasonal curve rather than a single warm afternoon. 8 of the 36 U.S. states we grade currently meet that bar. The rest are left blank instead of being filled in from one under-sampled lake.

No. Temperature is comfort, not bacteria, not cyanobacteria, and not a beach advisory. Pair this table with the lake’s nutrient readings and the current state advisory. An lake with low readings can still close after a bloom.