Dry Tortugas in December: Weather, Water Temperature, Crowds and a Two-Day Plan

DRY TORTUGAS · DECEMBER · THE MONTH GUIDE

December puts Dry Tortugas in its easy register. The average high at the nearest official weather station is 77.7°F, the sea off the islands averages 77.6°F at its daily peak, and hurricane season ended on November 30. Fort Jefferson’s brick walls, the moat and the snorkeling water around Garden Key are all on the table for a trip planned now.

The trade-off is light. On December 15 the sun rises at 7:02 a.m. and sets at 5:42 p.m. local time, leaving about 10 hours 40 minutes of daylight for a park you can only reach by boat or seaplane from Key West. Plan the crossing around the daylight, and keep one spare day in case the wind closes the water.

On this page

• Dry Tortugas weather in DecemberHighs of 77.7°F, lows of 68.3°F, 3.1 rain days
• Can you swim at Dry Tortugas in December?Yes, the sea peaks at 77.6°F on average
• How crowded is Dry Tortugas in December?What we know about holiday weeks, booking and lodging tax
• Things to do at Dry Tortugas in DecemberFort Jefferson, Garden Key and the snorkeling water
• A two-day Dry Tortugas plan for DecemberKey West sunset at 5:42 p.m., then the crossing
• December vs November or January at Dry TortugasHow the sea moves from 81.2°F to 76.5°F
• Is December a good time to visit Dry Tortugas?Who should go, and who should pick November

A word on the thermometer first. Every air figure here is a NOAA NCEI official normal for 1991 to 2020, measured at the Key West weather station, 70 miles east of the park. Dry Tortugas stands alone in open Gulf, windier and with nothing between it and incoming weather. Read the normals below as the closest real thermometer, and expect the island itself to feel breezier.

Dry Tortugas weather in December: average highs, lows and rain days

NOAA’s National Centers for Environmental Information put the December average high at 77.7°F and the average low at 68.3°F, with 2.16 inches of precipitation over the month. These are station normals from a real instrument at Key West (station USW00012836), averaged over 1991 to 2020. They are not a satellite or model estimate for the island. On a boat 70 miles out, add wind to whatever the Key West number says.

An average December brings 3.1 days with at least a tenth of an inch of rain. Spread over 31 days, that works out to measurable rain on roughly one day in ten. For a single day trip, the odds favor a dry crossing and a dry walk along the moat wall. If showers do come, a light rain shell in the day bag covers them.

The gap between the average high and low is 9.4°F. That sounds small, but the boat leaves Key West in the cool of the morning, closer to the 68.3°F low, and the open water adds wind. Pack a long-sleeved layer or a windbreaker for the ride out, and swimwear and reef-safe sunscreen for midday on Garden Key.

On December 15 there are about 10 hours 40 minutes of daylight. Sunrise comes at 7:02 a.m. and sunset at 5:42 p.m. Eastern time. A day trip that returns to Key West in the afternoon lands with little light to spare. Anyone camping on Garden Key should have the tent up and dinner sorted before 5:42 p.m.

Can you swim in Dry Tortugas in December? Water temperature

Yes. The Open-Meteo Marine API puts the sea surface off Dry Tortugas at an average of 77.6°F in December, over 2015 to 2024. That figure is the mean of daily maxima, the warmest reading of each day. It runs a shade warmer than a 24-hour average would, so early-morning water sits a little below it.

In practice, the water in December matches the air: 77.6°F at sea against a 77.7°F average high at Key West. Most snorkelers get in without hesitation at midday. People who chill easily, or who plan long sessions over the reef, tend to bring a thin wetsuit top or rash guard. Swim in the warmest hours, late morning to mid-afternoon, and dry off in the sun afterward.

Our sources hold no wind or swell data for the islands in December. What they do say is that Dry Tortugas sits in open Gulf, windier than Key West and exposed to whatever weather arrives. Check the marine forecast the evening before the crossing, and ask your boat or seaplane operator about their weather policy when you book.

How busy is Dry Tortugas in December? Crowds and prices

We found no visitor-count or fare series for Dry Tortugas by month, so we rank no December week as cheap or expensive. Across the state, our Florida orientation flags the holiday weeks as annual crowd peaks and early December as a quieter stretch. That pattern is statewide, and we could not confirm it for the park itself.

The park is reached only by boat or seaplane, so seats on the crossing are the limit. We could not verify ferry capacity or typical booking lead times, so we give no number of weeks. The safe order is to book the crossing first, then the Key West nights around it, and to book earliest for dates near the holidays.

Most visitors sleep in Key West, in Monroe County. We could not verify the county’s lodging-tax rate, so we give no percentage. Ask for the all-in nightly price, taxes and fees included, before you confirm a room. Our Florida trip-cost guide covers how resort fees and parking stack up.

If one line of the budget deserves extra money in December, make it flexibility on the crossing. A rebookable or refundable seat, plus a spare Key West night, lets you move the trip by a day if the wind picks up. The Key West station normals tell you nothing about sea state at the island, so the spare day matters most.

Things to do in Dry Tortugas in December

December pairs swimmable water with a quieter sky. The sea averages 77.6°F at its daily peak, rain falls on about 3.1 days, and the Atlantic hurricane season closed on November 30. November still falls inside that season, and January water runs a degree cooler, at 76.5°F on the same Open-Meteo measure.

The core of any visit is Fort Jefferson on Garden Key: the brick fort itself, the walk along the moat wall, and the snorkeling in the shallows off the beach. Farther out, Loggerhead Key and its lighthouse stand on the horizon. We could not verify entrance fees, opening hours or campground rules for these sites, so none appear. The National Park Service publishes them, and our Florida national parks guide sets the park against the state’s others.

What December changes is the gap between water and air. In November the sea peaks at 81.2°F, well above November’s 81.0°F average high at Key West. By December the two meet, at 77.6°F and 77.7°F. The fort walk is cooler work in December, and the swim loses 3.6°F of warmth.

We could not verify any free-entry days or no-cost programs at the park for December, so we name none. The sunset from the Key West waterfront the evening before your crossing costs nothing, and at 5:42 p.m. on December 15 it fits before dinner.

Dry Tortugas in December: a two-day itinerary

Day one, Key West. Fly or drive in (our Florida flights guide sorts the airports) and check in early. Walk the old town in the morning while it sits near the 68.3°F low. Confirm your crossing seat and the next day’s marine forecast by midafternoon, then head to the waterfront for the 5:42 p.m. sunset. Lay out the windbreaker, swimwear and sunscreen before bed.

Day two, the crossing. Sunrise is at 7:02 a.m. Be at the dock well before your departure, wearing a layer for the wind. On Garden Key, tour Fort Jefferson first, then snorkel through the warmest hours, when the water nears its 77.6°F peak. If the wind cancels the boat, swap the days: spend day two in Key West and cross on day one’s spare morning, or add a night. The Key West guide fills a lost day.

Dry Tortugas in December vs November and January

Air figures come from the Key West station normals for 1991 to 2020. Sea figures come from the Open-Meteo Marine API over 2015 to 2024, a different source and period. From November to December the average high drops 3.3°F, the low 3.9°F and the sea 3.6°F. From December to January the drop slows: 1.9°F on the high, 2.8°F on the low, 1.1°F in the water. December carries the most rain by volume, at 2.16 inches, while January has the most rain days, at 3.3.

Moving four weeks earlier, to November, buys 81.2°F water and 81.0°F highs. The catch is that November sits inside hurricane season, which runs to November 30. Moving four weeks later, to January, costs 1.1°F of sea warmth and brings 65.5°F lows for the dawn crossing, in exchange for 0.33 inch less rain. Our November and January guides carry the full detail.

Is December a good time to visit Dry Tortugas?

Yes, for most travelers. Snorkelers comfortable in water at 77.6°F, fort visitors who want mild 77.7°F afternoons, and anyone who prefers to travel after hurricane season will find December a good fit. It suits people less well if they have one fixed day and no room to move it: with no wind data for the island, a spare day is part of the plan.

Swimmers who want the warmest water should look at November. Its sea averages 81.2°F, 3.6°F above December’s. Book it with flexible terms, since the month falls before the November 30 end of hurricane season. Our Florida best-time guide lays out the full year.

Of these three months, December is the one that falls outside hurricane season and still keeps the sea above 77°F.

The last word

The one decision that shapes a December trip is how much slack you build around the crossing. Rain is unlikely to spoil it: the Key West station records an inch or more on just 0.7 day in an average December. Wind is the unknown. Book a rebookable seat, keep a spare Key West night, and plan to be snorkeling off Garden Key while the water nears its 77.6°F peak.

Sources & data for this guide

• December, November and January air normals (highs, lows, precipitation, rain days), 1991 to 2020 · NOAA NCEI monthly normals, Key West station USW00012836, 70 miles east of the park · checked Sep 24, 2026
• Sea surface temperature, mean of daily maxima, 2015 to 2024 · Open-Meteo Marine API · checked Sep 24, 2026
• Daylight, sunrise and sunset on December 15 (12:02 and 22:42 UTC, shown here in Eastern time) · sunrise-sunset.org · checked Sep 24, 2026
• Hurricane season end date and statewide holiday crowd pattern · our Florida orientation, citing NOAA National Hurricane Center
• Our sources hold no wind or swell data for the islands, and we could not verify ferry or seaplane fares, park fees, opening hours, booking lead times or the Monroe County lodging-tax rate · check the National Park Service and your operator when you book.

To plan your stay

• Best Time to Visit Dry Tortugas: Weather, Sea Temperature and the Quiet Months
• Dry Tortugas in January: Weather, Sea Temperature, Crowds and a Two-Day Plan
• Dry Tortugas in November: Weather, Sea Temperature and Crowds
• Dry Tortugas in February: Weather, Sea Temperature and Crowds

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