KEY WEST · AUGUST · 24.55° N
The thermometer at Key West International Airport averages a high of 90.6°F in August and a low of 80.5°F, and the water off the island runs 88.8°F. That pairing is what people book the month for and what they grumble about by noon: swimming that needs no acclimation at all, and a walk down Duval that does.
August also sits inside the Atlantic hurricane season, June 1 to November 30, whose most active stretch runs from mid-August to mid-October and peaks on September 10, per NOAA’s National Hurricane Center. None of that makes the month unbookable. It makes a refundable rate and a look at the tropics in the week before your flight the sensible way to book it.
THE MONTH AT A GLANCE · KEY WEST · AUGUST
August buys the warmest water of the summer and an 8 p.m. sunset, in exchange for 90.6°F afternoons, nine wet days and a place inside the busiest weeks of hurricane season.
AVG HIGH 90.6°F · SEA 88.8°F · 5.37 IN OF RAIN · 13H 01M OF DAYLIGHT
Go for: water at 88.8°F from breakfast to dusk, Fort Zachary Taylor at $2.50 on foot, and the Mallory Square sunset celebration, which runs every night of the year.
Think twice before: booking non-refundable or planning midday sightseeing on foot: the most active hurricane weeks start mid-month, and the average afternoon reaches 90.6°F.
Climate: NOAA NCEI 1991-2020, Key West International Airport · Sea: Open-Meteo Marine · full sources at the end
On this page
- Key West weather in AugustHighs of 90.6°F and 9.1 wet days
- Can you swim in August?Sea surface at 88.8°F
- Crowds, booking and the lodging taxMonroe County’s 5% rental tax, and what sells out
- Things to do in the heatFort Zachary Taylor, the Hemingway Home, Dry Tortugas
- A two-day plan for AugustTwo days built around an 8 p.m. sunset
- August, July or September?How the three months compare
- Is August a good time to go?Who should go, and who should shift the dates
Every figure here has a named owner. The temperature and rain normals come from the NOAA station at the airport, the water reading from a marine model rather than a dockside thermometer, the ferry and museum prices from the operators themselves. Where two sources disagree, as they do on the Duval Loop timetable and on the length of US-1, we give the range rather than picking a winner.
Key West weather in August: average highs, lows and rain days
| Measure | August normal | On the ground |
|---|---|---|
| Average high | 90.6°F | Above 90 most afternoons |
| Average low | 80.5°F | Nights stay warm, the AC runs |
| Precipitation | 5.37 in | Spread across 9.1 wet days |
| Days with 0.10 in or more | 9.1 | Roughly one day in three |
| Days with 1.00 in or more | 1.4 | One or two real soakings |
| Daylight, Aug 15 | 13h 01m | Sunrise near 7 a.m., sunset just after 8 p.m. |
| Sea surface | 88.8°F | Mean of daily maxima, 2015-2024 |
Those are station normals, measured on the island. NOAA’s National Centers for Environmental Information publish them for Key West International Airport, station USW00012836, over the standard 1991-2020 period: average high 90.6°F, average low 80.5°F, 5.37 inches of rain for the month. A gridded reanalysis would hand you slightly different values for the same patch of ocean and asphalt, and it would not be a thermometer.
That 5.37 inches reads worse than it lives. Measurable rain falls on 9.1 days in an average August, about one day in three, and only 1.4 days bring an inch or more. Florida’s wet season delivers its water in concentrated afternoon storms rather than all-day drizzle, as our state timing guide lays out, so the working assumption for an August day is a bright morning, a loud hour somewhere between two and five, and a usable evening.
Ten degrees separate the day figure from the night one, and the night one is still 80.5°F. Nothing in the bag needs to be warm. What the month asks for is a spare shirt, a hat, a rain shell light enough to carry all day, and shoes you can rinse out. Old Town is flat, compact and the largest wooden historic district in North America, so most days end with more walking than anyone planned.
On August 15 the island gets 13 hours and 1 minute between sunrise and sunset, with the sun up around 7 a.m. and down just after 8 p.m. (sunrise-sunset.org, converted to Eastern time). A sunset that late leaves room for a full afternoon indoors and a long evening outside afterward. The Sunset Celebration at Mallory Square starts about two hours before sundown, runs until dusk has faded, and happens every night of the year, weather permitting.
Can you swim in Key West in August? Sea temperature and what it feels like
The sea surface off Key West averages 88.8°F in August in the Open-Meteo Marine record for 2015-2024, and the number carries an asterisk: it is the mean of daily maxima, so it describes the water at its warmest point in the day rather than an average across 24 hours. Call it a shade warmer than what you step into at seven in the morning, and a shade warmer than tables built on 24-hour means.
In practice, 88.8°F means entry is instant and there is no acclimation ritual at the waterline. A two-hour snorkel needs no wetsuit, children stay in until they are called out, and the rash guard you wear is protecting you from the sun rather than the cold. The one thing this water cannot do is fix a 90.6°F afternoon. You come out of it warmer than you went in, and the shade does the rest of the work.
We could not verify monthly wind or swell averages for the waters off Key West, so we give no figures for either. What the calendar does say is that the most active weeks of the hurricane season begin mid-August, and a system several hundred miles away can turn a flat week choppy with a day’s notice. The ferry to Dry Tortugas crosses 70 miles of open water, so take that day early in the trip and leave a spare day behind it.
How busy is Key West in August? Crowds, booking windows and the Monroe County rental tax
Florida’s crowd peaks are the holiday weeks and spring break, and the Keys run their headline season from December to May, as our state orientation puts it. August belongs to neither. We found no monthly occupancy or room-rate series for Monroe County, so we crown no month cheapest and quote no discount: what we can say is that the island’s busy calendar sits in winter, not now.
What still needs booking ahead is the boat. The Yankee Freedom III leaves at 8 a.m. daily, check-in before 7:30, at about $250 for an adult in 2026, park entrance, snorkel gear, breakfast and lunch included. It sells out weeks out, so reserve a month ahead at least. Key West has its own airport, EYW, and if you drive instead, count roughly three and three-quarter to four hours from Miami without stops, six to eight with them.
On the room itself, Monroe County levies a 5.0% transient rental tax, filed and paid alongside the 6% state sales tax (Florida Department of Revenue, form DR-15TDT). Eleven percent on a $300 night is $33 before any resort fee or parking charge appears, and those are separate line items that vary by property. Our Florida cost guide handles the wider budget.
The upgrade that genuinely changes an August day is a bed you can walk home to. Street meters run $3.00 an hour. The Old Town Parking Garage charges $6 an hour or $48 a day plus tax, the Mallory Square lot $7 an hour or $48 a day with a ten-hour cap, the Key West Bight lot $5 an hour or $40 a day (City of Key West rates, subject to change). Sleeping inside Old Town turns the car into a one-time expense parked for the week.
Things to do in Key West in August: Fort Zachary Taylor, the Hemingway Home and Dry Tortugas
What August gives that the dry-season months cannot is water at 88.8°F paired with a sun still up at eight, which adds up to a snorkel at breakfast, a swim after dinner, and no jacket at any point in between. The cost is the middle of the day. Between roughly eleven and four, the shade, the AC and the indoor hours carry the schedule, and a plan that ignores that fact falls apart by Tuesday.
Fort Zachary Taylor Historic State Park holds the beach most often called the island’s best and sits within walking distance of Old Town: $2.50 on foot or by bicycle, $4.50 for a single-occupant vehicle or motorcycle, $6.00 per vehicle for up to eight people plus a $0.50 county surcharge each. The gate opens at 8 a.m. and closes at sundown, 365 days a year, and the fort itself shuts at 5 p.m. The Ernest Hemingway Home and Museum takes walk-ins 9 a.m. to 5 p.m. daily, $19 adult, $7 child, free under 6.
August does not move those opening hours, it moves the clock you use them on. Fort Zachary Taylor at 8 a.m. gives you sand before the heat arrives, and the fort at four gives you thick masonry and shade with an hour to spare. The Hemingway house is the indoor hour the middle of the day needs, cats included: the museum traces them to Snow White, the writer’s polydactyl cat. Dry Tortugas, 70 miles west with no road or bridge, is at its warmest for snorkeling now.
Free in August, as in every month: the Sunset Celebration at Mallory Square, which begins about two hours before sunset and holds until dusk fades. The Duval Loop bus is also free, with 18 stops through Old Town, though our sources disagree sharply on its hours, from every 20 minutes between 8 a.m. and 10 p.m. in one account to every 15 minutes until midnight in another. Read the stop sign, and note it does not serve the airport. Mile Marker 0 costs nothing either, at Whitehead and Fleming, where US-1 begins its 2,370 miles or so north to Fort Kent, Maine.
Key West in August: a two-day itinerary
Day one runs on the light. Be at Fort Zachary Taylor when the gate opens at 8, swim while the air is still in the low eighties, and be back in Old Town before eleven. Lunch indoors and slowly. Take the Hemingway Home between one and three, well ahead of the 5 p.m. cutoff for walk-ins. Shower, then reach Mallory Square around six, two hours before an 8 p.m. sunset. Dinner happens after dark, when the air finally settles toward its 80.5°F floor.
Day two is the boat day: check-in before 7:30 a.m. for the 8 o’clock sailing, back on the dock mid-afternoon with lunch already behind you. If the forecast turns, remember the shape of August rain, 1.4 days in an average month bringing an inch or more, most of it in a concentrated hour. Trade the crossing for the museum, a slice of key lime pie (invented here in the late nineteenth century, built on sweetened condensed milk, named Florida’s official pie in 2006), and Old Town on foot between showers.
Key West in August vs July and September
| Measure | July | August | September |
|---|---|---|---|
| Average high | 90.2°F | 90.6°F | 89.0°F |
| Average low | 80.6°F | 80.5°F | 79.2°F |
| Precipitation | 3.63 in | 5.37 in | 7.24 in |
| Days with 0.10 in or more | 6.8 | 9.1 | 10.2 |
| Sea surface | 88.7°F | 88.8°F | 88.3°F |
| Hurricane season | Inside it, quieter half | Most active weeks start mid-month | Statistical peak, Sept 10 |
| Note | Detail |
|---|---|
| Same source for all three columns | NOAA NCEI 1991-2020, station USW00012836, plus Open-Meteo Marine for the sea. No column is estimated. |
August is the hottest of the three by four tenths of a degree on the daytime figure, 90.6°F against July’s 90.2 and September’s 89.0. Rain climbs in a straight line across the summer, 3.63 inches, then 5.37, then 7.24, and wet days follow it, 6.8 to 9.1 to 10.2. The water barely notices any of this: 88.7, 88.8, 88.3. Whichever of the three you pick, you are swimming in the high eighties.
Move back four weeks to July and you drop 1.74 inches of rain and 2.3 wet days for the same heat and the same water, with the quieter half of hurricane season around you. Move forward to September and you add 1.87 inches and 1.1 wet days, and you land on the season’s statistical peak of September 10, in return for afternoons 1.6°F cooler. Four weeks either way changes the rain and the risk far more than the thermometer.
Is August a good time to visit Key West?
Yes, if the trip is built on water and evenings, and if the booking can move. Swimmers, snorkelers, divers and anyone happy to spend the middle of the day indoors get the best water of the year and an island out of its winter rush. No, if the dates are locked and unrefundable, if the plan is walking tours at noon, or if a canceled ferry would wreck the week.
If that second description fits, the answer is not September, which is wetter and sits on the season’s peak date. It is the dry season: our state orientation gives the Keys a December-to-May window, when the rain drops away, the water clears, and the hurricane calendar is closed. You pay for it in room rates and company, and where you sleep matters more then than it does now.
No other month puts 88.8°F water under a sun that stays up past eight o’clock, and that combination is worth surrendering a few afternoons to the air conditioning.
The last word
Book the room you can walk home to, take the Tortugas ferry early in the week rather than on your last morning, and give the hours between eleven and four to shade. One thing to know before you picture an empty summer waterfront: the three limits Key West voters approved in November 2020, a cap of 1,500 disembarking cruise passengers a day, a ban on ships carrying more than 1,300 people, and docking priority for the best environmental records, were nullified by SB 1194, written to apply retroactively. The ships still call, in August as in February.
Sources & data for this guide
- August normals, rain days and the July and September columns · NOAA NCEI monthly normals 1991-2020, station USW00012836, Key West International Airport · checked Sep 23, 2026
- Sea surface 88.8°F, mean of daily maxima 2015-2024 · Open-Meteo Marine API · checked Sep 23, 2026
- Daylight, sunrise and sunset for August 15, converted to America/New_York · sunrise-sunset.org · checked Sep 23, 2026
- Hurricane season dates, September 10 peak, mid-August to mid-October activity · NOAA National Hurricane Center · checked Sep 23, 2026
- Transient rental tax 5.0% plus 6% state sales tax · Florida Department of Revenue, form DR-15TDT · checked Sep 23, 2026
- Fort Zachary Taylor hours and entry fees · Florida State Parks · checked Sep 23, 2026
- Hemingway Home hours and fares · hemingwayhome.com · checked Sep 23, 2026 · the Snow White lineage is the museum’s own account, our only source on it
- Yankee Freedom III sailing time, check-in and 2026 adult fare · drytortugas.com · checked Sep 23, 2026 · fares change
- Meter, garage and lot rates · City of Key West Parking Department · checked Sep 23, 2026 · rates change
- Duval Loop, free, 18 stops, no airport service · City of Key West and local guides · checked Sep 23, 2026 · sources disagree on frequency and hours, so we give the range
- US-1 terminus at Whitehead and Fleming, mileage to Fort Kent · Atlas Obscura and Key West Travel Guide · checked Sep 23, 2026 · published totals run from about 2,369 to 2,390 miles
- November 2020 cruise referendum and SB 1194 preemption · Seatrade Cruise and Florida Politics · checked Sep 23, 2026
- We found no monthly occupancy or room-rate series for Monroe County, so we name no cheapest or busiest month and quote no discount. Afternoon-storm timing is editorial, drawn from the wet-season pattern, not from a measured hourly series.
To plan your stay
- Things to Do in Key West: Hours, Prices, Hemingway House and the Dry Tortugas Ferry
- Where to Stay in Key West: Old Town, New Town and What Parking Costs
- Key West Airport to Old Town: Transfers, Parking and the Drive from Miami
- What to Know Before You Go to Key West: Parking, the Free Duval Loop, Sunset and the Dry Tortugas Ferry