There is no single “best month” for every visitor.
The right time depends on whether you care most about calmer water, cooler air, birding, camping, trip availability or flexibility around wind.
For boat comfort
NPS boating guidance says summer is generally calmer and rainier, while winter tends to bring more high-wind days and drier weather. Travelers prioritizing the smoothest possible boat conditions often focus on the calmer-season pattern, while still understanding thunderstorms and tropical weather can occur.
For winter travel
Winter can bring comfortable air temperatures and heavy visitor demand, but wind can affect offshore boat days. Camping transportation also becomes more competitive during busy winter periods.
For birding and wildlife
Dry Tortugas is a major stopover for migratory birds, so seasonal birding interest can be a reason to time a visit differently from a beach-focused traveler. Current NPS alerts and wildlife guidance should be checked close to travel.
For availability
The “best” date is useless if your preferred transportation is sold out. For visitors with fixed vacation dates, securing the boat, ferry or seaplane first can be more important than chasing an idealized month.
For private charters
A private-boat traveler should keep a weather-flexible mindset. Offshore conditions can cause changes even when the park itself is open. Booking policies and fallback options deserve as much attention as average climate.