September weather in Costa Rica: the complete guide
September in Costa Rica?
The Pacific coast is at peak rainfall — not ideal for beach holidays. The Caribbean coast (Puerto Viejo, Cahuita) hits its annual dry window with clear, sunny days. Green turtle nesting peaks at Tortuguero. Prices are at their annual lowest. The month rewards travellers who plan around what it offers.
September in Costa Rica: the month most people misread
Ask a tourism agency when to skip Costa Rica and September will be near the top of the list. They are looking at Pacific rainfall data, which is accurate: September is the wettest month on Costa Rica’s Pacific slope. What they are not mentioning is the other side of the continental divide, where September is one of the best months of the year.
The Caribbean coast — Puerto Viejo, Cahuita, Tortuguero — experiences its relative dry season in September-October. The same atmospheric pattern that dumps rain on the Pacific redirects moisture away from the Caribbean. While Guanacaste is receiving its heaviest rainfall of the year, Puerto Viejo might have five sunny days in a row. This is not coincidence — it is a predictable consequence of how the Inter-Tropical Convergence Zone and northeast trade winds shift across the country in these months.
September rewards travellers who understand this geography. This guide maps it honestly.
The Caribbean coast in September: the best month
The Caribbean coast’s September dry window is not widely publicised. Most mainstream travel advice focuses on Pacific weather and ignores the seasonal flip that the Caribbean experiences. The result is that September sees some of the lowest visitor numbers on the Caribbean side, combined with some of the best weather conditions — a genuine anomaly.
In Puerto Viejo and Cahuita in September:
- Many days see morning sunshine through early afternoon with minimal rain
- Beach days at Punta Uva, Playa Cocles, and Cahuita’s National Park beach are genuinely reliable
- The Caribbean sea is calm in September mornings — flat enough for paddleboarding and relaxed swimming
- Reef snorkelling visibility at Cahuita peaks when the dry window reduces freshwater runoff
Cahuita National Park’s reef is the longest living coral reef on Costa Rica’s Caribbean coast. In September, when rainfall is minimal on the Caribbean side, visibility at the snorkelling sites can reach 8-15 metres — among the best conditions of the year. The reef supports parrotfish, angelfish, sea turtles, eagle rays, and occasional nurse sharks. An experienced local guide helps navigate which sections are accessible depending on sea conditions on any given day.
The Afro-Caribbean culture of Puerto Viejo is equally vibrant in September. The food scene — pati (flaky meat pastries), rice and beans cooked in coconut milk, whole snapper grilled on beach stalls — does not diminish in shoulder season. The reggae bars are open. The pace is slow. And hotel prices are well below what they charge in December or during Semana Santa.
Getting to the Caribbean from San José takes 4-5 hours by shuttle (approximately $65 per person with Caribe Shuttle or similar operators). The road through Braulio Carrillo National Park is one of Costa Rica’s most dramatic, dropping from cloud forest highlands to humid Caribbean lowlands in about an hour.
Tortuguero in September: turtle nesting continues
Green sea turtle nesting at Tortuguero peaks in August and continues into September. The nesting season runs officially from July through October, with August-September seeing the highest nesting activity. By mid-September, nesting frequency begins to decline from its August peak but remains significant enough to make September turtle watching nights rewarding.
Tortuguero: sea turtle tour — from $50Tortuguero National Park’s canal system is excellent in September regardless of turtle activity. The canals are at full water level after months of rain, expanding the waterway network and making boat access to more remote sections easier. Morning boat tours encounter caimans, green iguanas, three-toed sloths, river otters (occasional), boat-billed herons, and kingfishers. Manatees are occasionally reported in the slower sections of the canals.
The logistics of Tortuguero are slightly unusual compared to most Costa Rica destinations. There are no roads to the village — access is by boat (typically from Cariari, via a connecting bus from San José) or by small plane. Tortuguero village itself is a strip of wooden buildings along the beach and the canal. The lodges (Pachira Lodge, Mawamba, Tortuga Lodge) sit across the canal from the village and include meals and tours in their rates. The all-inclusive structure makes Tortuguero pricing straightforward to compare.
Pacific north (Guanacaste) in September: the honest picture
September in Guanacaste is genuinely the Pacific’s most challenging month. Liberia averages 200-250 mm, and unlike August’s afternoon shower pattern, September can bring more sustained multi-hour rain events. Some days bring overcast mornings in addition to the afternoon rain.
This does not make Guanacaste impossible in September — it makes it specifically for flexible, value-driven travellers. Hotel occupancy in Tamarindo and Playa Conchal drops to 15-30% in September. The savings are substantial: properties that charge $200-300 per night in January list at $80-130 in September. The beaches exist, the restaurants are open, most activities run. You need weather flexibility built into each day.
The Rincón de la Vieja area specifically is worth flagging: some trails in the national park can be partially closed after heavy September rain. The main Las Pailas thermal zone remains accessible, but the longer circuits through the park require checking conditions. The access road to the park from Liberia stays passable year-round on the main route.
Tamarindo in September is a specific case: the surfing community stays active because the Pacific swells are at their strongest. Intermediate and advanced surfers who want serious wave conditions find September optimal. Beach tourism — sunbathers, snorkellers, casual swimmers — is far less reliable.
Central Pacific in September: activity-focused, not beach-focused
Manuel Antonio in September is wet but functional for wildlife-focused visitors. The national park’s biodiversity is unchanged by the month — the sloths do not care about the rain calendar. September visitor numbers in Manuel Antonio are so low that some weekdays see fewer than 60 visitors in the entire park. The wildlife viewing quality from a disturbance standpoint is exceptional.
The Jacó surf scene continues in September, though some beginner-oriented operations scale back due to stronger swells. The bioluminescence boat tours that operate from Jacó’s estuary area run year-round and are atmospheric in September — the mangrove boat rides through the bioluminescent water happen after dark regardless of Pacific weather.
Quepos and the surrounding area has some good mid-range accommodation that discounts significantly in September. Using Quepos as a base for Manuel Antonio park visits, Damas Island mangrove kayaking, and a catamaran trip on calm September mornings creates a reasonable Pacific itinerary even in the rainiest month.
Southern Pacific in September: Uvita and whale season ending
The southern hemisphere humpback whale season runs through October, with September marking the gradual end of the busiest phase. Whale watching from Uvita in early September is still good — mother-calf pairs remain in the waters around Marino Ballena. By late September, whale density decreases as the population begins moving south. Book whale watching for early September rather than late if this is a priority.
September weather on the Southern Pacific is heavy. The Osa Peninsula and the Uvita area receive 350-450 mm in September — the wettest month for this region. Road conditions to some remote Osa locations can be challenging. Unpaved roads south of Dominical and toward Drake Bay require 4WD in September.
Caño Island snorkelling from Uvita in September is weather-dependent and more variable than in dry season. Pacific swells can make the boat crossing rougher than in January. That said, reputable operators monitor conditions and cancel if the sea is unsafe — this is appropriate, not disappointing.
La Fortuna and Arenal in September: hot springs in the rain
La Fortuna receives consistent rainfall in September, but the activity infrastructure is built for it. The La Fortuna Waterfall is at maximum flow in September — the 500-step descent to the pool base leads to a falls running at full cascade volume. This is one of the most photogenic versions of the waterfall available. Mornings often have brief clearing that makes the descent comfortable before afternoon clouds move in.
Hot springs near Arenal are year-round operations and are genuinely more appealing in rainy season than in high season: soaking in geothermal water while watching rain fall through jungle canopy is one of the small pleasures of a wet-season Arenal visit. Both Tabacón and Ecotermales operate year-round. Rates at most La Fortuna hotels are 25-30% below January in September.
The hanging bridges in the Arenal area — Mistico Park, the newer Arenal Hanging Bridges reserve — are excellent in September. The cloud forest environment is at maximum density, birds are active feeding before afternoon rain, and the elevated perspective over the rainforest canopy is stunning even in misty conditions.
The Ostional arribada: September wildlife spectacle
One of the world’s great wildlife events occurs on the Nicoya Peninsula in September through November: the Olive Ridley turtle mass nesting, known as the arribada. At Ostional beach, timed to the waning moon, hundreds of thousands of Olive Ridley sea turtles emerge from the ocean simultaneously to nest. A single September night at Ostional during an arribada can see an estimated 40,000 to 100,000 turtles on the beach at once.
Access to Ostional is strictly managed by the ADIO community cooperative. You must book through a licensed guide, typically arranged through operators in Nosara or Sámara — both about 30-40 minutes from Ostional. Tours depart at night when scouts confirm arrival activity. The experience is managed carefully to reduce disturbance: groups are small, lights are controlled, and guides enforce respectful behaviour.
The Ostional arribada is not predictable to the day — it follows the lunar cycle, and the largest events occur on the three-to-five nights around the waning moon. If witnessing the arribada is a priority, book a Nosara or Sámara hotel for a five-night window around the waning moon in September and maintain flexibility about which specific night you go.
Accommodation and pricing in September
September is the cheapest month for Pacific coast accommodation in Costa Rica. Savings are substantial and genuine:
| Travel style | Daily per person |
|---|---|
| Backpacker | $38-52 |
| Mid-range | $80-120 |
| Comfort | $150-240 |
| Luxury | $290-500+ |
Luxury eco-lodges — Lapa Rios at Drake Bay, Nayara Springs at Arenal — discount 20-30% in September. Budget hostels in La Fortuna and Jaco may run $18-25 per night for dorm beds. The Caribbean coast does not discount as steeply because September is actually their good-weather period — some Caribbean properties charge standard rates or close to it in September-October.
September itinerary strategy
The strongest September itinerary leans Caribbean:
Days 1-3: Puerto Viejo and Cahuita — Caribbean dry window, reef snorkelling, Punta Uva beach Days 4-6: Tortuguero — sea turtle nesting night tours, canal boat wildlife Days 7-9: La Fortuna — waterfall, hot springs, hanging bridges (morning activities before rain) Day 10: Return to San José, optional Orosi Valley or La Paz Waterfall Gardens day trip
For a shorter 7-day Caribbean focus: Days 1-4: Puerto Viejo, Cahuita, Manzanillo Days 5-7: Tortuguero
Avoid building a September trip around Guanacaste beach holidays unless you have genuinely flexible plans and the savings are the primary motivation.
What to pack for September
- Waterproof rain jacket with hood — an umbrella alone is not sufficient in sustained Pacific rain
- Quick-dry synthetic clothing for everything; cotton is impractical in wet season
- Waterproof bag liner or dry sack for cameras, passport, electronics
- Trail shoes or sandals with closed toes and good grip on wet surfaces
- Insect repellent (more insects in wet season, important at Tortuguero especially)
- A compact inflatable dry bag for snorkelling equipment (Caribbean)
- Light jacket for Monteverde and highland visits (cooler in cloud forest year-round)
Frequently asked questions about September weather in Costa Rica
Is September the worst month to visit Costa Rica?
Only for Pacific beach holidays. It is one of the best months for the Caribbean coast, Tortuguero turtle watching, and value travel across the country. September requires honest planning: avoid Pacific beach resort expectations and instead build the trip around what September delivers — wildlife, waterfalls at full flow, extraordinary marine life on the Caribbean, and significantly lower costs.
Why is the Caribbean dry when the Pacific is wet?
The Caribbean dry window in September-October results from a shift in the Inter-Tropical Convergence Zone. When northeast trade winds reassert in September, Caribbean moisture is redirected. Simultaneously, the Pacific is still receiving heavy rain from westerly moisture systems. The continental divide separates these two systems, creating opposite conditions on each coast in the same week.
Can I visit Corcovado in September?
Yes, with significant planning and flexibility. September is Corcovado’s wettest month, and trail conditions are extreme — genuinely muddy, with river crossings potentially difficult after heavy rain. The Sirena station access occasionally requires checking current SINAC conditions. It is doable for experienced wilderness travellers who are prepared for full wet-jungle conditions. A licensed guide is mandatory for Sirena visits and essential for safety in September.
What is the Olive Ridley arribada?
The mass nesting event at Ostional beach, synchronised with the waning moon, when hundreds of thousands of Olive Ridley turtles nest simultaneously. September arrivals are among the largest of the year. Access is managed by the ADIO community cooperative through licensed guides. It is one of the most extraordinary wildlife spectacles in the Americas. See our Tortuguero guide and Nosara guide for relevant context.
Should I book travel insurance for September?
Travel insurance is advisable any month, but September specifically carries higher weather risk for flight disruptions, road closures (particularly in the Osa Peninsula), and outdoor activity cancellations. Ensure your policy covers activity cancellation due to weather and check whether evacuation coverage applies if you are visiting remote areas like Drake Bay or Corcovado.
Frequently asked questions
Is September a good time to visit Costa Rica?
It depends entirely on where you go. The Caribbean coast in September is among the best travel conditions of the year — sunny, clear, and with the lowest prices. The Pacific side is at peak rainy season and suits only flexible travellers comfortable with wet afternoons. Tortuguero turtle nesting and Caribbean snorkelling make September excellent for wildlife-focused visitors.
Where to go in September?
The Caribbean coast is the clear answer: Puerto Viejo, Cahuita, and Tortuguero all hit their relative dry window in September-October. Cahuita reef snorkelling reaches peak visibility. Tortuguero's green turtle nesting is still active. On the Pacific side, La Fortuna and Monteverde work well for activity-based trips where rain does not spoil plans.
What about rain in September?
September is the wettest month across the Pacific slope. Guanacaste can receive 200-250 mm; the Osa Peninsula 350-450 mm. Rain falls mostly in the afternoon and evening on the Pacific. The Caribbean coast flips this pattern — September is one of the driest months there, with many sunny, clear days due to the shifting trade wind pattern.
How much does it cost?
September is the cheapest month to visit Costa Rica. Accommodation on the Pacific coast runs 40-50% below January rates. Budget travellers can get by on $38-55 per day. Mid-range comes in at $80-120. Even luxury eco-lodges discount 20-30% in September. The Caribbean does not discount as steeply because September is actually their peak conditions month.
What about wildlife in September?
Green turtle nesting at Tortuguero is still active in September, though tapering from August's peak. Olive Ridley turtles at Ostional begin their mass arrivals (arribada). Humpback whale watching at Uvita continues from August but is winding toward its seasonal end. Caribbean reef fish and snorkelling conditions peak at Cahuita. Caño Negro birding is excellent.