The quick answer
If your trip is built around the Pacific coast, the Central Valley, Guanacaste, Arenal or Monteverde, the driest and most predictable months run from roughly December into April. If it is built around the Caribbean coast, that advice is close to backwards: Limón, Cahuita, Puerto Viejo and Tortuguero are usually at their brightest around September and October, which are the two wettest months almost everywhere else in the country.
Most visitors never hear this, because the country is normally described as though it had one season. It does not.
Why the two coasts disagree
A mountain spine runs the length of the country and separates two entirely different weather systems. The Pacific side dries out when the trade winds settle into their winter pattern and soaks through the middle of the year. The Caribbean side faces those same trade winds directly and takes moisture off the sea all year, with its heaviest rain around the middle of the year and again toward the end of it, and a genuine lull in between.
The Instituto Meteorológico Nacional treats these as separate climate regions with separate outlooks, and that is the right way for a traveler to think about them too. Ask what the weather does where you are going, in the month you are going, rather than what it does in Costa Rica.
The dry season on the Pacific side
Roughly December to April. Reliable sun, dusty roads in Guanacaste, brown hillsides by March, and the highest prices and busiest parks of the year. Christmas, New Year and the week before Easter are the three periods when Costa Ricans travel domestically in large numbers, so the coast fills with national as well as international visitors and accommodation is booked out furthest ahead.
The green season, which is not a euphemism
From roughly May to November the Pacific and Central Valley move into the season Costa Ricans call invierno and the tourism industry calls green. In much of the country, for much of that period, this means bright mornings and a heavy shower in the afternoon rather than continuous rain. The forest is loud and full, the rivers are high, waterfalls are worth the walk, rates drop, and the parks are quiet.
September and October are the exception on the Pacific side and are genuinely wet, with the strongest chance of a day lost to weather and of a road or a trail closing. They are also, for the same meteorological reason, the best window on the Caribbean.
The Caribbean calendar
Limón province keeps its own rhythm. Expect rain in any month, because this is a rainforest coast. But the drier, sunnier windows fall around September and October, and to a lesser extent in February and March. If you want the Caribbean beaches, the reef at Cahuita, Puerto Viejo and the canals at Tortuguero at their best, September and October are the months to build around, and they have the additional advantage of being quiet.
What else the month decides
Wildlife
Turtle nesting is seasonal and species-specific, and the seasons differ by coast: Tortuguero on the Caribbean and the Pacific nesting beaches do not run to the same calendar. Whale watching on the Pacific has two distinct seasons because populations arrive from both hemispheres. Ask about the species and the beach rather than about the country, and check the current arrangements with SINAC, which sets access and guide requirements at each site.
Surf
The Pacific swell is generally biggest in the middle of the year, which is the wet season. The Caribbean’s best surf is generally around the turn of the year. The two are, again, opposite.
Roads and access
Unpaved routes deteriorate in the wet months and some become genuinely difficult. This affects Monteverde, the Osa Peninsula and the Caribbean south more than it affects the main corridors. It is a reason to plan slightly fewer moves in the green season rather than a reason to stay away.
Planning with LABUSA Travel
We will tell you plainly what your month usually does on your route, and where a route crosses the mountain spine we will tell you that you are asking about two climates rather than one.
Sources
- Instituto Meteorológico Nacional: the national weather service, including regional forecasts and the seasonal outlook for each climate region. Accessed 11 August 2026.
- Instituto Costarricense de Turismo: the national tourism board, including official entry guidance and protected-area visitor information. Accessed 11 August 2026.
- SINAC, Sistema Nacional de Áreas de Conservación: the national protected-area system, which sets opening arrangements, capacity limits and access rules for every national park. Accessed 11 August 2026.