Best Month to Swim, by State — Typical Lake Temperatures

8 U.S. states currently have enough A- and B-graded lakes with Water Quality Portal monthly temperatures to name a typical swim month. 6 of those states land on July. This is climatology — typical for the month — not a live satellite skin temperature, and not a beach clearance.

Driving the news

8 of 36 U.S. states we grade have at least three A/B lakes with monthly surface-temperature climatology. The rest are omitted rather than guessed.
Minnesota’s typical most-comfortable month on A/B lakes is July, median about 75°F, from 384 lakes.
Florida’s A/B set names May (median about 81°F) because later summer typical readings often sit above a 68–82°F comfort band. Warm is not the same as comfortable, and comfortable is not the same as safe.

Typical month, not “water temp today”

lake.com’s “best time to visit” lists are built from visitor reviews. LakeMonster titles lake pages with a satellite skin temperature and the word “today.” We have a national climatology, not a national live layer. USGS live lake-temperature gauges cover a few dozen waterbodies. Publishing “today” on thousands of lakes without a gauge would be a title lie. This report uses the honest number we do have: typical surface temperature by month, from EPA Water Quality Portal field samples, on lakes that already earn an A or B nutrient-and-algae grade.

The comfort band is 68–82°F. If a state has at least one month whose median typical temperature among A/B lakes sits in that band, that month wins. If every sampled month is colder or hotter, the warmest sampled month wins and the table still shows the median, so a reader can see why. Per-lake monthly charts remain on each best-times lake page.

Best typical swim month, by state

Florida is first alphabetically, not “best.” Median °F is the median of that month’s typical surface readings across the A/B lakes that have the month. Sample size is the number of those lakes, not the number of individual bottles.

State	Typical month	Median °F	A/B lakes with temps
Florida	May	81	326
Iowa	July	81	19
Michigan	July	66	27
Minnesota	July	75	384
Missouri	August	82	39
North Dakota	July	72	8
New York	July	73	3
Wisconsin	July	77	240

28 U.S. states we grade do not yet have three A/B lakes with enough monthly bins. Canada and European bathing waters are outside this table; 38 jurisdictions are graded in total, and this question is a U.S. summer-swim story.

What this does not tell you

A typical July of 75°F on Minnesota A-grades does not mean every Minnesota lake is 75°F on July 15 of this year. It does not mean the beach is open. It does not mean cyanobacteria are absent. Use the lake page for the letter grade, the climatology chart, and any live gauge, then check the state advisory the morning of the trip. For same-day E. coli dots, Swim Guide remains the specialist; we join that question to a multi-year grade rather than trying to replace their volunteer network.

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 A- and B-graded Minnesota lakes with enough monthly samples, the typical most-comfortable month is July at about 75°F. Florida’s A/B 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. The numbers are typical surface temperatures by month, aggregated from EPA Water Quality Portal field samples across many years. A live USGS gauge reading, where one exists, is on the lake’s own page and is dated. Copying “water temp today” without a live reading would be a different — and false — claim.

A state appears only if at least three A- or B-graded lakes there have three or more monthly climatology bins. 8 of 36 U.S. states we grade currently clear that bar. Missing is missing: we do not invent a swim month 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 grade and the current state advisory. An A-graded lake can still close after a bloom.