Costa Rica in May: Green Season Proper, Whale Season Opens, and the Country Goes Lush

May is when Costa Rica’s green season is fully established. The Pacific side receives consistent afternoon and evening rain that transforms the landscape — the brown, desiccated vegetation of March becomes the luminous green that makes Costa Rica look like a country designed for postcards. Humpback whales from the Northern Hemisphere arrive in Costa Rican Pacific waters in May (the Southern Hemisphere population arrives August–October, making Costa Rica unique in hosting two distinct humpback seasons). Prices remain 25–40% below January peak. The country is running at full capacity but without the crowds.

Weather & Conditions

Guanacaste: 25–34°C. Consistent afternoon rains. Mornings typically clear.

Manuel Antonio: 24–31°C. More rain than Guanacaste. Lush conditions.

Arenal: 20–26°C. Rainy season conditions. Waterfalls at peak flow.

Osa Peninsula (Corcovado): 24–32°C. Heavy rain. Trails more challenging. Wildlife excellent.

Caribbean coast: 24–30°C. This is the Caribbean’s wet season — conditions variable.

What to Do

Humpback whale watching (northern population), Drake Bay and Dominical: From May through October, humpback whales from the Northern Hemisphere (North Pacific population) arrive in Costa Rica’s Pacific waters to breed and calve. The Drake Bay and Dominical areas on the Pacific coast offer the best whale watching. Operators in Drake Bay (Aguila de Osa, Drake Bay Wilderness Resort) run morning whale watching tours. In September–October, the Southern Hemisphere humpbacks arrive, briefly overlapping with the northern population and creating a unique double-season.

Arenal waterfalls at peak: The La Fortuna Waterfall (70m, accessible via a 500-step descent from the road above) reaches its maximum flow in May and continues through the rainy season. The water is cold but the volume is extraordinary. The Río Celeste (in Tenorio Volcano National Park, north of Arenal) — a turquoise-blue river colored by sulfur and calcium compounds — is also at maximum color and flow.

Corcovado in the green season: May Corcovado is challenging — the trails are muddy, the rivers run high, and the rain is genuine. The wildlife, however, is exceptional — animals are active, breeding, and feeding. The howler monkey troups, scarlet macaw pairs, and Central American tapirs are all present. The experience requires proper wet-season preparation (rubber boots, dry bags, waterproof layers) and a higher tolerance for physical challenge, but delivers wildlife encounters that the dry season’s manicured trails don’t always provide.

River rafting — peak season: May river levels make the Pacuare and Sarapiquí rivers exceptional for whitewater rafting. Class III–IV rapids at maximum flow on the Pacuare (one of National Geographic’s top rafting rivers) are the standard May experience. Multi-day Pacuare trips with overnight camping in the jungle river canyon run through all rainy season months.

Monteverde green season: The cloud forest is at its most cloud-like in May — the mist is persistent, the epiphytes are dripping, and the sense of immersion in the forest is total. The wildlife activity is excellent. The famous hanging bridges and canopy walks run in all weather.

Festivals & Events

Labor Day (May 1): National public holiday. Limited services and domestic travel.

Mother’s Day (second Sunday of August — check the date): Not a travel-impacting event but reflects the country’s busy family culture.

Practical Tips

Green season rain pattern: May rain is typically heaviest in the afternoon (2–6pm) and continuing into the evening. Morning activities (wildlife tours, hiking, boat trips) are largely unaffected. The “veranillo” (little summer) — a brief dry spell in late June to early August — occasionally provides a break in the rain.

Corcovado May: rubber boots (the knee-high style) are essentially required for the trails after significant rain. The park entrance stations rent them for visitors who arrive without. River crossings can be deep and fast after heavy rain — follow ranger guidance.

Car rental: book with road clearance in mind. Many remote routes to Osa, beaches, and Corcovado access points become difficult or impassable for low-clearance vehicles. A 4WD is strongly recommended for May travel outside main highways.

Who May Is For

Humpback whale watching visitors targeting the northern population. Green season value travelers who want the country lush and at low prices. Whitewater rafting enthusiasts who need river flow. Advanced wildlife travelers who accept mud and rain for exceptional wildlife concentration. And budget-focused travelers who understand that May’s conditions are genuinely good for most activities.