Labor Day gets a bad rap. Folks drain the pool, fold the towels, and act like the water went cold overnight. It didn’t. Across a wide stretch of the country, lakes soak up heat all summer and hang onto it like a cast-iron skillet long after the crowds pack up. September is the quiet payoff: warm water, an empty boat ramp, and sunlight that turns gold by four in the afternoon. We’ve pulled together the lakes where a mid-September swim isn’t wishful thinking. It’s just a good decision nobody else is making. Grab the paddleboard.
Please note that some of the imagery in this article may have been enhanced with the assistance of AI.
39. Lake Havasu, Arizona, California, Sun-Baked Coves Along the Colorado River
Havasu is the stubborn one. It stays warm because the desert around it won’t really cool until October, and the Colorado River moving through keeps it clean. Surface temps hold in the upper 70s through September. Bathwater, by lake standards.
Here’s the catch nobody mentions. The sun is brutal even when the air feels fine, and you’ll burn on the water inside an hour without noticing until that evening. Pack more shade and more sunscreen than you think you need. The coves on the Arizona side run calmer and warmer than the main channel, where boat traffic kicks up chop well into fall.
38. Shasta Lake, California, Warm Arms Winding Between Mountain Slopes
Shasta sprawls into five main arms, and those arms are the whole trick to a late-September swim. The narrow fingers like the Pit and McCloud warm up faster and hold heat better than the wide open main body near the dam.
Surface water sits in the low-to-mid 70s this time of year. Not Havasu warm, but comfortable, and the air stays hot in Redding long after the calendar says fall. Rent a houseboat, tie off in a quiet cove, and you’ll have swimming water most people assume closed for the season. One warning. Watch the exposed shoreline, because when the reservoir drops in late summer the banks turn steep and slippery.
37. Lake Travis, Texas, Limestone Coves That Hold Summer’s Heat
Central Texas doesn’t get the memo about September.
The air hangs in the 90s well past Labor Day, and all that pale limestone ringing Travis soaks up heat and feeds it back into the water. Surface temps stay in the upper 70s to low 80s deep into the month.
Let’s say this plainly: Travis is a drought lake. The level swings hard year to year, and a low lake means ramps close and coves disappear, so check the current level before you load the boat. When it’s full, the coves off the main basin hold some of the best warm swimming water in the state.
36. Lake Ouachita, Arkansas, Clear, Island-Dotted Water in the Ouachita Mountains
Ouachita is the cleanest big lake you’ve probably never swum in. Most of the shoreline has no commercial development, there are hundreds of small islands, and the water is clear enough that scuba divers come here to train.
That clarity pays off for September swimmers. The water stays comfortable, often mid-70s, and the mountain setting lets the air cool off nicely in the evening without chilling the lake. Pick an island cove, drop anchor, swim off the boat. Once the summer crowds thin out, you’ll likely have the whole rock to yourself.
35. Sand Hollow Reservoir, Utah, Red-Sand Beaches and Brilliant Blue Water
The color combination here does half the work. Blue water against red Navajo sandstone and red-sand beaches, like somebody painted it on purpose. Sand Hollow sits in Utah’s warm southwest corner near St. George, where September still feels like summer and the water stays in the low-to-mid 70s.
The reservoir runs shallow and sandy-bottomed in its swim areas, so it warms fast and stays warm. Watch your feet though. That red sand gets hot enough at midday to make you hop, so bring something to wear on the beach. A great spot for families who want warm water without the drive to a big-name destination.
34. Lake Martin, Alabama, Island-Dotted Water and Rocky Swimming Coves
Alabama summer doesn’t quit in September, and Lake Martin is the lake it lingers on. Warm green water studded with islands, pine forest right to the edge, and smooth granite outcrops the locals jump off all season.
Surface temps hold in the upper 70s to low 80s through the month. Chimney Rock and the cliff-jumping spots stay busy, but the quieter rocky coves on the back channels are where you want to float. The swimming’s easy, the water soft, a slightly warmer tea-colored Southern reservoir feel that the Lake Martin regulars will recognize immediately. Plenty of launch points, and the crowds thin out fast once school starts.
33. Lake Mohave, Nevada, Arizona, Clear Swimming Coves in the Mojave Desert
Mohave is the narrow blue ribbon below Hoover Dam’s reservoir, running between Davis Dam and Lake Mead. The desert around it bakes right through September, and the lake holds its warmth in the sheltered coves.
What most people miss: the water near the river channel can run surprisingly cold, released from deep in the dam upstream. The swimming coves and the southern end stay warm, often mid-to-upper 70s. Telephone Cove and the spots around Katherine Landing are your reliable bets. Clear water, quiet beaches, and almost nobody around once the summer crowds finally clear out.
32. Lake Murray, South Carolina, Warm Water Around Small Islands
Central South Carolina stays muggy and warm into fall, and Lake Murray holds that heat in its water. Low islands scatter across a wide, shallow-shouldered lake just outside Columbia.
Surface temps stay in the upper 70s to low 80s through September. The small islands carve out pocket coves where the water goes still and warm, perfect for anchoring and swimming off the back of the boat. And there’s one genuine oddity worth knowing about. The lake hosts a huge roost of purple martins on Bomb Island in late summer, thousands of birds wheeling in at dusk, a show worth timing a swim around. Then they head south, and so does the swimming season, eventually.
31. Lake Amistad, Texas, Clear Blue Water Along Desert Canyon Walls
Way out near Del Rio, where Texas runs up against Mexico, Amistad sits in desert country that stays hot long past the calendar’s say-so. The water is strikingly clear and blue, backed by limestone canyon walls that drop straight into it.
September water temps hold in the upper 70s to low 80s. The canyons make for shaded, cool-looking coves that are actually warm to swim in. It’s remote, so you’ll need to be self-sufficient on fuel and supplies, but that remoteness is the gift. Find a canyon cove and swim with no boat traffic in sight. Bring everything, because the nearest anything is a drive.
30. Broken Bow Lake, Oklahoma, Clear, Pine-Fringed Coves in the Ouachitas
Tucked in Oklahoma’s pine-covered southeastern corner, Broken Bow looks more like a Rocky Mountain lake than anything you’d expect from the state. Clear green water, tall pines right to the edge, rocky coves that go quiet once the Hochatown cabin crowd clears out.
Water temps hold in the mid-70s through September, warm enough for a comfortable swim and cool enough to feel refreshing on a hot afternoon. The clarity is the selling point, and you can see the rocky bottom well below the surface in the coves. Pair a morning swim with a cabin in Hochatown and you’ve got about the easiest shoulder-season lake trip in the region. Water this clean, air this warm, and the summer renters already gone home.
29. Lake Berryessa, California, Sun-Warmed Coves in Napa County’s Dry Hills
Berryessa heats up like a cast-iron pan and holds it. Those dry Napa hills have no shade to speak of, so the water banks sun all summer and stays swimmable well into September, often warmer than it has any right to be that late in the year.
Head for the quieter arms near Pope Creek or the Narrows. The main basin gets choppy with afternoon wind and ski-boat wake, but the coves stay glassy in the morning. Go early, swim before the breeze picks up around noon, and you’ll have water that feels like a bath.
28. Norris Lake, Tennessee, Turquoise Channels Winding Through Forested Hills
People fly past Norris on their way to the Smokies and miss one of the cleanest lakes in the South. The water runs genuinely clear, a true green-blue in the sun, and it holds warmth into early fall thanks to all that protected channel water tucked between the ridges.
The shape does the work here. Norris is all fingers and arms, so wind rarely builds across open water. You find a cove, drop anchor, and swim off the back of the boat in water that feels warmer than the lake average by a good margin.
27. Saguaro Lake, Arizona, Swimmable Water Beneath Red Cliffs
Thirty minutes from Phoenix and it feels like a different planet. Saguaro sits in the Salt River chain, ringed by red cliffs and actual saguaro cacti standing guard on the slopes. The desert keeps the air warm long after Labor Day, so September swimming here is dependable in a way the northern lakes just can’t touch.
Near the dam the water runs cooler and deeper. Stick to the shallower fingers and the designated swim beach, where the sun has had all day to work on the shallows.
26. Lake of the Ozarks, Missouri, Protected Coves With a Long Swim Season
The Ozarks lake runs over a thousand miles of shoreline, almost all of it broken into coves, and that geography is the whole story for late-season swimming. Tucked-away water heats through the summer and lets it go slowly, so the protected spots stay comfortable into mid-September most years.
Here’s what nobody tells you: the main channel is a highway. Weekend boat traffic throws real wake and the water can turn murky near the busy stretches. Find a quiet cove off the Gravois or Niangua arm, away from the big marinas, and swimming becomes a completely different experience.
25. Lake Keowee, South Carolina, Blue Foothill Water With Mountain Views
Keowee is the one that looks like a travel brochure and actually delivers. Clear deep-blue water, the Blue Ridge piled up in the distance, and a swim season that stretches into fall because the Carolina upstate stays warm late.
The water is clearer than most people expect from a Southern lake, almost unnervingly so when you peer down from a paddleboard. Deep and cool in the main channel, warmer in the shallow coves by afternoon. We’d pick a sandy cove near one of the state park access points and swim from shore.
24. Elephant Butte Lake, New Mexico, Long Beaches in the Chihuahuan Desert
New Mexico’s biggest lake sits out in the open desert south of Socorro, and that location is exactly why you can swim here when the mountain lakes have already gone cold. The Chihuahuan Desert holds heat late, and Elephant Butte’s long sandy beaches stay warm through September.
It doesn’t look like the other lakes here. No forested coves, no cliffs crowding the water. Just big sky, pale sand, and miles of open shoreline where you can walk a hundred yards from the next family and have the water to yourself.
23. Possum Kingdom Lake, Texas, Warm Water Around Dramatic Cliffs
Texans drive right past the bigger reservoirs to get to Possum Kingdom, and the cliffs are why. Buff-colored limestone bluffs drop straight into clear water, and the famous twin bluffs at Hell’s Gate are the kind of thing you remember long after you’ve left.
The water runs clearer than most Texas lakes and stays warm through September in the sheltered coves. Deeper water near the bluffs is a little cooler, worth the swim when you want to shake off a hundred-degree day. And north Texas hands you plenty of those well past summer.
22. Table Rock Lake, Missouri, Arkansas, Warm Coves Beneath Forested Hills
Table Rock is the clean-water cousin of the busier Ozark lakes to the north. The water runs clear and green, the hills crowd right down to the shore, and the deep coves hang onto their summer warmth into September.
Whatever you do, don’t swim off the main channel near Branson. The pretty swimming hides in the quieter arms, where you wade off a gravel bank into water clear enough to watch the bottom drop away beneath you. Morning is best. The surface goes to glass before the day-trip boats show up.
21. Lake Anna, Virginia, Piedmont Coves With a Swim Season That Runs Into Fall
Lake Anna has a quirk that stretches its swim season. Part of it gets fed by warm-water discharge from a power station, which keeps the so-called “hot side” noticeably warmer than you’d ever guess. Even on the public side, the shallow Piedmont coves cling to their heat deep into fall.
It’s an easy drive from both Richmond and D.C., which makes it a weekend lake first and a destination second. Go midweek in September and the crowds thin right out, leaving you warm coves and plenty of elbow room.
20. Inks Lake, Texas, Calm Coves Framed by Pink Granite
Inks is the small, calm one in the Highland Lakes chain, and its secret is the pink granite. The same rose-colored rock that built the Texas capitol rings this lake and soaks up heat like a radiator, keeping the shallows warm into September.
Because Inks sits at a nearly constant level year-round, the state park here has swimming you can actually plan a trip around. The coves are calm, the water is clear over the granite, and it never gets the wild weekend wake of the bigger Highland Lakes. An easy, low-stress pick.
19. Lake Lanier, Georgia, Sandy Beaches and Warm Coves Near Atlanta
Thirty minutes out of Atlanta traffic and you’re standing on actual sand. Lanier hangs onto its warmth longer than most people expect, and September here feels like a bonus round, the water holding in the upper seventies through much of the month. So the coves near the beaches at Van Pugh and Burton stay swimmable while the kids are already back in school.
Here’s what nobody tells you: Labor Day empties this lake out. The boats thin, the beaches open up, and the cove that felt like a parking lot in July suddenly belongs to you.
18. Lake Tenkiller, Oklahoma, Clear Water Along Steep Ozark Foothills
They call it Oklahoma’s clearest lake, and for once the nickname earns it. Tenkiller runs genuinely green and see-through, the kind where you can watch your own feet on a gravel bottom eight feet down. Scuba divers train here. That tells you everything about the visibility.
The steep Ozark foothills funnel the heat, so the water stays comfortable deep into September, and the snug coves on the eastern side warm fastest. Bring water shoes. The gravel is beautiful and it is not kind to bare feet.
17. Pickwick Lake, Tennessee, Alabama, Mississippi, Sandy Swimming Areas on the Tennessee River
Three states share this water, and all three agree it stays warm. Pickwick sits on a slow, wide stretch of the Tennessee River, and that steady flow plus Deep South latitude means the swimming beaches hold their warmth past Labor Day without much argument.
The sandbars are the draw. People anchor off them, wade out waist-deep on a firm sandy bottom, and let the current do nothing much at all. Lazy water, in the best sense.
16. Folsom Lake, California, Golden Foothills and Accessible September Beaches
The hills around Folsom go gold by late summer, which looks hot because it is. That dry foothill heat keeps the reservoir warm enough to swim well into September, and the lake sits close enough to Sacramento that you can be in the water an hour after leaving the office.
Granite Bay and Beals Point have the easy beaches, with real parking and real sand. Watch the water line, though. By September a foothill reservoir can drop a long way, and the shore you remember from June might be a hundred yards further out.
15. Lake Texoma, Texas, Oklahoma, Sandy Islands and Broad Swimming Beaches
Texoma is big water. One of the largest reservoirs in the country, straddling two states, and it behaves more like an inland sea than a lake. The sandy islands are the signature, little patches of beach you boat out to, drop anchor beside, and wade onto like you found something.
September cools the air before it cools the water, so the afternoons turn pleasant while the swimming beaches stay warm. Wind can kick up fast across that much open surface, so keep an eye on the far shore.
14. Dale Hollow Lake, Tennessee, Kentucky, Clear Coves Along a Rugged Shoreline
Dale Hollow guards its coves. The shoreline is rugged and folded, so you weave a boat back into a slot of water that feels private even on a busy weekend, with a clarity that rivals anything east of the Mississippi.
Those deep, protected coves trap summer warmth, and the southern Tennessee side stays swimmable through most of September. It’s a quieter, wilder lake than the names further south. Fewer beaches, more coves you earn by boat.
13. Lake Mead, Nevada, Arizona, Warm Desert Water Beneath Towering Canyons
Desert water does something different. Lake Mead sits in the Mojave, surrounded by bare red canyon walls that bake all summer, and the reservoir stays warm into October, never mind September. Swimming here in fall feels almost too easy.
Boulder Beach is the simple entry point near Las Vegas. That pale mineral band high on the canyon walls tells the drought story at a glance, so check current conditions and launch access before you load the car. But the water that’s there is warm, open and blue in a way that stops you for a second.
Few places let you swim in warm open water with red desert canyons rising straight out of it. This is one of them.
12. Sam Rayburn Reservoir, Texas, Quiet Swimming Coves Among Tall Pines
Big Sam is Texas pine country, the largest lake entirely inside the state, ringed by the kind of tall East Texas pines that drop a carpet of needles right to the water’s edge. It smells like warm resin on a September afternoon.
The coves run quiet here. This is a fishing lake first, so swimmers get the place mostly to themselves, the water warms easily, and the protected fingers stay comfortable late. Watch for the old standing timber in the shallows. It’s part of the character and it will bark your shin.
11. Smith Mountain Lake, Virginia, Mountain-Framed Coves That Retain Summer Warmth
Twenty thousand acres, and more shoreline than you’d ever guess from a map, all of it folded into coves. Smith Mountain Lake sits low enough in the Virginia foothills to stay warm while the mountain views cool everything else down, and the protected arms hold heat into mid-September easily.
A settled, friendly lake with real waterfront towns around it. The swimming is cove swimming, warm and still, with the Blue Ridge hazing blue in the distance behind you.
10. Canyon Lake, Texas, Clear Hill Country Water Beneath Limestone Bluffs
The clearest water in Texas sits here. Cold springs and limestone keep Canyon Lake green and transparent in a way the state’s muddier reservoirs never manage, pale bluffs rising off the shore while the Hill Country rolls out behind them in cedar and rock.
September is the sweet spot. The brutal Texas summer backs off, the crowds thin, and the water stays plenty warm for long afternoons in the coves. Overlook Park gives you the postcard view and easy water access.
9. Lake Guntersville, Alabama: Warm Tennessee River Water Beneath Appalachian Ridges
Guntersville is a Tennessee River impoundment, and that’s exactly why it swims so well so late. River reservoirs hold a huge volume of water that soaks up heat all summer and releases it slowly, so the shallows near the coves can still run low 80s when the mornings have started turning crisp.
Sixty-nine thousand acres of it, tucked under the ridges of northeast Alabama. The bass fishermen know this lake cold, but the swimming coves on the north side stay bath-warm into fall. Show up after the holiday weekend and most of them are yours.
8. Lake Norman, North Carolina: Broad Swimming Water North of Charlotte
The biggest man-made lake in North Carolina, and close enough to Charlotte that half the metro treats it as a backyard. That proximity cuts both ways. Summer weekends get busy — but by mid-September the pontoon traffic thins out and the water’s still holding comfortable heat.
Thirty-two thousand acres gives you room to find a quiet cove. Aim for the public access points on the less-developed northern end, away from the restaurant docks, where a swim doesn’t come with a boat wake every ninety seconds.
7. Greers Ferry Lake, Arkansas: Clear Water Around Ozark Bluffs
You can see your feet here. Greers Ferry is one of the clearer lakes in the region, running that clean Ozark blue-green that makes you forget you’re in Arkansas and not somewhere with a passport stamp.
The clarity comes at a small cost. Clear water sits a touch cooler than the murky stuff, because sunlight dives deeper instead of warming the top layer. It still swims great through September — the coves around Sugar Loaf Mountain hold their heat, and the bluff-lined sections hand you that cliff-jumping-if-you-dare scenery without the resort-lake mob.
6. Lake Hamilton, Arkansas: Warm Resort Water Near Hot Springs
Hamilton is the resort lake, the one with the cottages and the lakeside restaurants and the boat you rent by the hour. Built for leisure, and it shows.
Sitting in the Ouachita foothills just south of Hot Springs, it runs a little warmer than its mountain cousins. The water stays genuinely comfortable into the first couple weeks of fall, and the resort docks mean you can swim, dry off, and walk to a plate of catfish without changing out of a wet suit. No roughing it required for a late-season swim.
5. Kentucky Lake, Kentucky and Tennessee: Warm Shallows Along Wooded Peninsulas
This is one of the biggest reservoirs east of the Mississippi, and the long fingers of wooded peninsula create exactly the kind of shallow, protected water that bakes warm all summer.
Those shallows are the move. Deep open water takes forever to cool, sure, but the sandy flats off the peninsulas warm fast each morning and stay kind to kids and cold-averse grandparents well into September. Land Between the Lakes gives you miles of undeveloped shoreline, so a quiet beach isn’t hard to come by. The only real decision is which state’s side of the water you’re splashing in.
4. Lewis Smith Lake, Alabama: Clear Water Beneath High Forested Bluffs
Smith Lake surprises people. Tucked into north Alabama, it runs deep and clear with high bluffs that funnel the water into green ribbon-like arms, and it looks more like a mountain lake out west than anything you’d expect down here.
The water is clean enough to see down a good way, and the bluff coves hold summer warmth into the shoulder season. Fair warning, though — the deeper main channel stays cool year-round, so you want the shallower back ends of the creek arms for an actual warm swim. Find one of those and September is some of the best water you’ll touch all year.
3. Kerr Lake, North Carolina and Virginia: Long Beaches and Warm Piedmont Water
Most reservoirs give you rocks and docks. Kerr gives you actual sand beaches, long stretches of them, which is rarer than it sounds and a big part of why this one’s worth the drive to the state line.
Straddling the Carolina and Virginia border, it’s warm Piedmont water with real swimming areas you don’t have to scramble down a bluff to reach. The designated beaches slope in gently, toddler-safe and sun-warmed deep into September. Bring chairs. This is a lay-out-a-towel-and-stay-all-day lake, not a quick-dip kind.
2. Lake Powell, Utah and Arizona: Sandstone Inlets With Warm September Water
The outlier on this list, and the most spectacular. Powell is a desert reservoir carved through red sandstone canyons, the kind of place that looks painted rather than photographed.
Desert sun does the work here. Daytime air still pushes into the 90s in early September, and the slot-canyon inlets trap warm water that stays genuinely swimmable — often among the warmest water on this list. The catch is the lake’s size and the long hauls between ramps, so this is a houseboat-or-committed-day-trip lake, not a pull-off-the-road swim.
1. Lake Marion, South Carolina: Warm Lowcountry Water Along Cypress-Lined Shores
Marion closes out the list because it holds its heat longer than almost anywhere else here. This is the South Carolina Lowcountry, where fall arrives late and reluctant and the shallow tannin-stained water stays warm well past when the northern lakes have packed it in.
The cypress give it a look you won’t find on a mountain reservoir — trees growing straight out of the water, Spanish moss hanging low over coves. The water reads dark from the tannins. Bothers some swimmers, charms others. We’re in the charmed camp. Late September here still feels like summer refusing to leave, and after Labor Day you’ll have the whole warm, moss-draped place nearly to yourself.