Pura Osa
The short answer
- Best weather: December to April (dry season); February and March are the driest.
- Best for whales: August to October and January to March.
- Best value: May and June: sunny mornings, green forest, low prices.
- Most difficult: October and November: the heaviest rain, and some closures.
Osa at a glance: the year in one table
Rain bars show the average monthly rainfall around the Golfo Dulce, the wettest part of the region; the Costa Ballena gets somewhat less. Two dots mean peak season, one dot means possible or starting.
Swipe the table sideways to see every month →
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 🌧️ Rain (mm) | 165 | 96 | 114 | 248 | 562 | 585 | 653 | 718 | 619 | 804 | 771 | 369 |
| 🐋 Humpback whales | ●● | ●● | ●● | ● | ● | ●● | ●● | ●● | ● | ● | ||
| 🐢 Sea turtles nesting | ● | ●● | ●● | ●● | ●● | ● | ||||||
| 🐦 Migrant birds | ●● | ●● | ●● | ● | ● | ●● | ●● | |||||
| 🏄 Big surf (Pavones, Matapalo) | ● | ●● | ●● | ●● | ●● | ● | ● | |||||
| 🥾 Easy Corcovado trails | ●● | ●● | ●● | ● | ● | ● | ● | ● | ● | |||
| 👥 Crowds and prices | ●● | ●● | ●● | ● | ● | ● | ●● |
Rainfall: monthly averages for Golfito (climate-data.org). Wildlife seasons are typical patterns and vary from year to year.
Month by month
January
Dry season in full swing, northern humpbacks arriving and the busiest weeks of the year until New Year. Book boats, Corcovado permits and lodges months ahead.
February
Usually the driest, sunniest month. Calm seas for Caño Island snorkeling, easy trails in Corcovado and northern whales off Uvita.
March
Hot and dry, with the last weeks of the northern whale season. Easter week (Semana Santa) often falls in March or April and fills beaches with Costa Rican families.
April
The transition: still mostly sunny, prices start to drop, the first south swells reach Pavones and the stone spheres of Finca 6 line up with the rising sun around this month.
May
The green season begins. Mornings are usually clear and rain arrives in the afternoon. The quietest month: the best prices and the forest turns bright green.
June
Long days, sunny mornings and afternoon showers. Good surf on the Golfo Dulce side and few visitors on the trails.
July
Southern humpbacks start arriving and turtles begin nesting. Costa Rican school holidays (usually two weeks in early July) bring local families to the coast.
August
The start of peak whale season off Uvita, with mothers and calves close to shore. Wetter afternoons, but many sunny mornings for boat tours.
September
Whales at their peak and the Festival de Ballenas y Delfines in Uvita (4–6 September in 2026). The spheres of Finca 6 line up with the sun again in late August and early September. Some lodges and restaurants close for holidays.
October
The wettest month. In recent years SINAC has closed Sirena and other Corcovado sectors for maintenance in October, and some lodges close. Whales and turtles are still around, and prices are at their lowest.
November
Still very rainy, but quiet and green. The last southern whales leave, northern migrant birds return and turtle releases continue at Punta Banco.
December
The rains ease through the month and the dry season begins. The first northern whales appear, and the Christmas and New Year holidays are the most expensive weeks of the year.
The best time for what you want to do
| If you want… | Go in |
|---|---|
| Corcovado and long hikes | December to April |
| Humpback whales | August–October · January–March |
| Snorkeling and diving at Caño Island | December to April (calmer, usually clearer water) |
| Sea turtles | July to December |
| Birdwatching | December to April (with northern migrants) |
| Surfing Pavones | April to October (south swells) |
| The sunrise alignment at Finca 6 | Around April · late August to early September |
| Low prices and quiet beaches | May, June and September |
Tips for the green season
- Plan boat trips and hikes for the morning; rain usually starts after lunch.
- Rivers rise fast after heavy rain. Never cross a flooded river or stream by car or on foot.
- Pack a light rain jacket, quick-dry clothes and a dry bag for boat trips. A 4x4 helps on gravel roads.
- Leave a spare day in your plans, especially if you fly or take a boat to Drake Bay.
- In September and October, confirm that your lodge and restaurants are open; some family businesses close for holidays.
Frequently asked questions
What is the best month to visit Osa, Costa Rica?
For dry weather and easy access to Corcovado, February and March. For whales, September (southern humpbacks, with the Uvita whale festival) or January to March (northern humpbacks). For low prices and few visitors, May and June, when mornings are usually sunny.
When is the rainy season in Osa?
From May to November, with the heaviest rain in September, October and November. Most days start sunny and rain arrives in the afternoon or evening. The Golfo Dulce side, around Golfito and Puerto Jiménez, is one of the wettest areas of Costa Rica, with more than 5,000 mm a year.
Is it worth visiting Osa in October?
Only if you are flexible. It is the wettest month, some Corcovado sectors and lodges may close, and boat trips can be cancelled by weather. In exchange you get whales, turtles, empty trails and the lowest prices. Check the Corcovado sector status before booking.
When can I see humpback whales in Osa?
Almost all year. Southern Hemisphere humpbacks visit from July to November, with a peak from August to October; Northern Hemisphere humpbacks visit from December to April. Dolphins are seen all year.
What is the water temperature in Osa?
Warm all year, around 27–29 °C (81–84 °F). Air temperatures are usually 21–28 °C on the coast, and it feels hotter because of the humidity.
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