Dry Tortugas in May: Weather, Sea Temperature, Crowds and a Two-Day Plan

DRY TORTUGAS · MAY · 70 MILES WEST OF KEY WEST

May is when the water off Dry Tortugas warms into the mid-80s. The sea surface there averages 84.6°F for the month, and the official normals from Key West give an average afternoon high of 85.9°F. For a trip built around snorkeling the moat wall of Fort Jefferson and swimming off Garden Key, that pairing sets the tone for the whole visit.

The calendar adds two more pieces. Mid-May brings about 13 hours 23 minutes of daylight, and the month closes before the Atlantic hurricane season opens on June 1. Rain still turns up, on roughly four days in an average May, usually as a short afternoon interruption to a warm, bright stretch.

On this page

• Dry Tortugas weather in MayHighs of 85.9°F, lows of 76.4°F, 4.1 rain days
• Can you swim at Dry Tortugas in May?Sea at 84.6°F, and why that figure reads warm
• How busy is Dry Tortugas in May?Boat seats, booking order and Key West lodging tax
• Things to do at Dry Tortugas in MayFort Jefferson, the moat wall and the Garden Key beach
• Two days at Dry Tortugas in MayDay one on Garden Key, day two from the 6:41 a.m. sunrise
• Dry Tortugas in April or June instead?April’s 79.8°F sea against June’s 6.4 rain days
• Is May a good time to visit Dry Tortugas?Yes for swimmers and campers, April for drier weeks

You cannot drive to Dry Tortugas: the islands sit seventy miles west of Key West, reached by ferry, seaplane or private boat. Most trips start with a flight into the Keys (our Florida flights guide covers the airports) and a night in Key West before the crossing. Every climate figure here comes from the Key West airport station, so read the air normals as Key West conditions, with the islands likely windier and more exposed.

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

NOAA’s National Centers for Environmental Information publish 1991-2020 normals for station USW00012836 at Key West, a real thermometer and the closest official one we could use. For May it records an average high of 85.9°F, an average low of 76.4°F and 3.12 inches of precipitation. These are station readings seventy miles east of Fort Jefferson, and no gridded reanalysis stands behind them.

An average May logs 4.1 days with at least a tenth of an inch of rain, so measurable rain arrives about one day in seven or eight. The other six or seven days of each week are dry at the station. A wet day in practice means a shower to wait out under the fort’s brick arches, and most of a day on the island survives it.

Nights stay warm: the gap between the 85.9°F high and the 76.4°F low is 9.5°F. A sleeping bag is overkill for campers, and a light sheet or liner does the job. The bag should hold sun protection instead: a hat, a long-sleeved rash guard and reef-safe sunscreen, plus more drinking water than feels necessary on a warm day.

On May 15 the sun rises at 6:41 a.m. and sets at 8:05 p.m. Eastern Daylight Time, about 13 hours 23 minutes of daylight. Campers on Garden Key get the soft light at both ends of the day. Day-trippers see the fort in the harder midday hours between their boat’s arrival and departure.

Can you swim in Dry Tortugas in May? Sea temperature and what it feels like

Yes. Open-Meteo’s Marine API puts the sea surface off Dry Tortugas at 84.6°F in May, averaged over 2015-2024. That value is a mean of daily maxima, the warmest reading of each day, so it sits a shade above a 24-hour average. Tables built on round-the-clock means will show a slightly lower number for the same water.

At 84.6°F, the sea is only 1.3°F below the average May high on land. Stepping off the Garden Key beach feels like moving from one warm room to another, with no cold shock to brace for. An early-morning swim meets water a little cooler than the daily-maximum figure. A rash guard earns its place for sun protection on long snorkels, since the water itself asks for no wetsuit.

Our sources carry no wind or swell data for May, so we give no wave height or wind speed. The station we rely on sits in Key West, and Dry Tortugas stands alone in open Gulf, windier and with nothing between it and the weather. Crossing and snorkeling conditions on your date are the operator’s call, so confirm with the ferry or seaplane company the evening before.

How busy is Dry Tortugas in May? Crowds and prices

We found no occupancy or fare series for Dry Tortugas, so we rank no month as cheap or expensive. The calendar still tells you where May stands: after the March spring-break rush that our Florida overview flags, and before the hurricane season that opens June 1. Our Florida trip-cost guide sets out lean, middle and high budget tiers for the Key West nights.

Everyone arrives by ferry, seaplane or private boat, and seats on the public options are limited. We could not verify how many weeks ahead May departures sell out, so we give no count. Book the crossing first, then the Key West hotel nights before and after it, and choose refundable rooms where the rate allows.

We could not verify the Monroe County lodging-tax rate that applies to Key West stays, so we give no percentage. When you book, ask for the all-in nightly total with taxes and any resort fee included.

Spend the extra on an overnight rather than a day trip if the budget stretches. A day trip runs on the boat’s timetable. An overnight on Garden Key, with camping gear and a confirmed return seat, adds the 6:41 a.m. sunrise and the 8:05 p.m. sunset of mid-May to the visit. We could not verify 2026 fares for either format, so check the operators directly.

Things to do in Dry Tortugas in May

May lets you spend hours in the water without getting chilled. The sea runs 4.8°F warmer than in April, and the month ends before June brings 6.4 rain days and the start of hurricane season. Long, unhurried snorkels are the activity this month suits best.

Fort Jefferson fills most of Garden Key: an unfinished brick fort with roofed casemate arches and an open top level looking over the islands. Around it runs the moat wall, a walkway on the water with snorkeling along its outer edge. The Garden Key beach is the easy entry point, in water that averages 84.6°F in May. We could not verify 2026 hours or fees, and our Florida national parks guide sets the park beside its neighbors.

The water changes most between April and May, while the air moves 3.3°F. At an average high of 85.9°F, the fort’s open top level is best walked in the morning. The casemates stay shaded through the day, and the late afternoon returns the moat wall to comfortable walking before the 8:05 p.m. sunset.

Once you are on Garden Key, walking the fort, the moat wall and the beach carries no separate charge that we know of. Ask the operator when you book about the park entrance fee and whether your fare includes it.

Dry Tortugas in May: a two-day itinerary

Day one. Take the morning crossing from Key West and walk the fort as soon as you land, starting with the open top level before the midday heat builds toward 85.9°F. Spend the middle of the day in the water off the Garden Key beach, then move into the shaded casemates. Save the moat wall for late afternoon and stay on it for the 8:05 p.m. sunset if you are camping. Without a campsite, make this the day trip and give day two to Key West.

Day two. Campers get the island at 6:41 a.m. sunrise, with time to snorkel the moat wall before the day boats arrive, then pack for the return crossing. If one of May’s 4.1 rain days lands on your trip, wait out the shower under the brick arches. If the operator reschedules the crossing, keep the Key West night flexible and use our Florida things-to-do guide for a mainland backup.

Dry Tortugas in May vs April and June

From April to May, the Key West station adds 3.3°F to both the high and the low, and the Open-Meteo sea figure climbs 4.8°F, from 79.8°F to 84.6°F. From May to June, the high rises another 2.8°F and the sea only 2.0°F, while rain days go from 4.1 to 6.4 and precipitation from 3.12 to 4.23 inches. The water gains most of its warmth in May, and the rain picks up in June.

Moving four weeks earlier to April gets you 2.8 rain days and nights near 73.1°F, at the cost of sea water nearly 5°F cooler. Moving four weeks later to June gets you 86.6°F water and costs you 2.3 extra rain days, plus a trip inside the hurricane season that starts June 1.

Is May a good time to visit Dry Tortugas?

Yes, for snorkelers, swimmers and campers: the sea at 84.6°F and more than 13 hours of daylight make long water days comfortable. May suits heat-sensitive travelers less well, since the average high reaches 85.9°F on an island with little shade outside the casemates. Families with young children can plan around it by keeping the fort for mornings, and our Florida with kids guide has more on pacing warm days.

If the heat or the rain count puts you off, choose April. It averages 82.6°F for the high and 2.8 rain days, and its 79.8°F sea is still pleasant for a snorkel with a rash guard.

Of the three months, May alone pairs sea water in the mid-80s with a date still before the June 1 start of hurricane season.

The last word

Secure the boat or seaplane seat before you book anything else, then build the Key West nights around it. After that, May mostly asks you to plan for warm water and the odd storm. An average May at the Key West station brings 0.9 day with an inch of rain or more, roughly one proper soaking per month, so a dry bag for the phone and camera belongs in the kit. The rest of the time, the fort’s brick walls and the 84.6°F water are yours from sunrise to sunset.

Sources & data for this guide

• May, April and June air normals, precipitation and rain days · NOAA NCEI monthly normals 1991-2020, station USW00012836 (Key West) · checked Sep 24, 2026
• Station scope · the Key West station sits seventy miles east of Dry Tortugas, and the islands are more exposed to wind and weather · checked Sep 24, 2026
• Sea surface temperature, April to June · Open-Meteo Marine API, mean of daily maxima 2015-2024 · checked Sep 24, 2026
• Sunrise, sunset and daylight on May 15 · sunrise-sunset.org, converted from UTC to Eastern Daylight Time · checked Sep 24, 2026
• Hurricane season dates · NOAA National Hurricane Center, via our Florida guides · checked Sep 24, 2026
• What we could not verify: ferry and seaplane fares, 2026 park fees and hours, booking lead times, the Monroe County lodging-tax rate, and wind or swell data for May. Check operators when you book.

To plan your stay

• Best Time to Visit Dry Tortugas: Weather, Sea Temperature and the Quiet Months
• Dry Tortugas in April: Weather, Sea Temperature, Crowds and a Two-Day Itinerary
• Dry Tortugas in June: Weather, Sea Temperature, Rain Days and Crowds vs May and July
• Dry Tortugas in March: Weather, Sea Temperature, Crowds and a Two-Day Itinerary

Nearby places

• Key West Travel Guide: Driving Down US-1, Old Town Parking Rates, Fort Zachary Taylor and the Cruise Ship Vote
• Everglades National Park: The Complete Visitor's Guide
• Big Cypress National Preserve: Dark Sky Park, Swamp Buggies and the $100 ORV Permit