Things to Do in Costa Rica in September

September rainfall makes the Rio Pacuare Central America's best whitewater run. The river carves through a Talamanca Mountains gorge where howler monkeys scream from canyon walls and toucans cross overhead between rapids. Class III-IV water in September runs faster and fuller than the tamer dry-season version most tourists see. The Turrialba put-in sits at roughly 600 m (1,970 ft) elevation. Morning air is cool enough that spray feels refreshing, not cold. Most full-day trips cover 28 km (17.4 miles) and include a riverside lunch where guides grill chicken over wood coals while you sit on volcanic rocks listening to the current. The gorge section between Huacas and Dos Montanas is the stretch you came for. Jungle closes overhead in a corridor so narrow it feels like a tunnel. September water levels make hydraulics more complex. Operators run smaller groups. Guides earn their tips. Book through licensed operators at least a week ahead. The best guides fill boats early in green season. See current rafting options in the booking section below.

Monteverde's cloud forest sits between 1,400 m and 1,800 m (4,590 to 5,905 ft) elevation. September's heavy mist and dripping canopy bring the forest's nocturnal life to the surface. Red-eyed tree frogs cling to heliconia leaves at eye level. Their crimson eyes reflect your headlamp. Tarantulas the size of your palm sit motionless on moss-covered trunks. Kinkajous, normally deep in the upper canopy, descend to lower branches when the mist thickens. Night walks in September feel different from dry-season walks. The moisture amplifies every sound. Hear the drip of condensation off bromeliads. Listen for the metallic clicking of glass frogs. The Monteverde toad calls with deep resonance. Air temperature drops to about 15°C (59°F) after dark at this altitude. The cloud forest earns its name. Visibility sometimes narrows to a few meters. Guides carry high-powered spotlights. They know which trees the olingo and two-toed sloths favor. Low tourist numbers help. Peak amphibian activity seals it. September night walks are arguably the single best wildlife experience available in Costa Rica this month.

September is prime nesting season on both coasts. Stand on a dark beach. Watch an olive ridley sea turtle the size of a coffee table drag herself from the surf. She digs a nest with her rear flippers. She deposits a hundred eggs. Then she hauls back to the ocean. This encounter rewires your sense of scale. At Ostional Wildlife Refuge on the Nicoya Peninsula, mass arribada events bring thousands of turtles onto the beach. These last three to seven nights. They cluster around the third-quarter moon. The smell of wet sand and salt concentrates in the humid night air. The sound is slow and rhythmic. Flippers scrape against volcanic grit. On the Caribbean side, Tortuguero's canals and black-sand beaches host green turtles through early September. Leatherbacks occasionally still arrive. Tortuguero requires a boat or small plane to reach. This filters out casual visitors. Beaches stay uncrowded even during active nesting. Both locations require a certified guide for nighttime beach access. Guides use red-filtered lights. They avoid disturbing the turtles. You walk in near-total darkness between nests.

The sky-blue river inside Tenorio Volcano National Park is surreal in any month. September's rain volume does two things dry season cannot. The waterfall crashes with enough force to throw mist 30 m (98 ft) into the air. The forest trail becomes a sensory corridor of wet earth, decomposing leaves, and sharp mineral tang. Volcanic springs give the river its color. The turquoise comes from volcanic minerals and sulfur interacting with calcium carbonate in the water. Saturation intensifies when the river runs high. The trail is roughly 6 km (3.7 miles) round trip. It is mostly flat with a steep descent to the waterfall viewpoint. In September you will likely share it with a handful of other visitors. January and February bring queues. The trail gets muddy. It runs ankle-deep in places. Rubber boots are available for rent at the park entrance. They are not optional. Morning arrivals before 9 AM catch the forest before the clouds lower. Light through the canopy hits the river at angles that make the color almost unbelievable. Tubing on the Rio Celeste downstream of the park has become increasingly popular. It runs well in September's higher water.

September's afternoon rain pattern makes this the ideal month for an indoor activity. Learn something worth keeping. The Central Valley around San Jose, Heredia, and Atenas grows most of what ends up on a Costa Rican plate. Cooking classes here start in the morning. They happen at farm-to-table operations. You pick culero peppers and cilantro coyote from the garden. Then you head into the kitchen. Learn to make gallo pinto properly. Toast the rice before combining it with yesterday's black beans. Finish with Salsa Lizano. This tangy brown sauce goes on everything. Visitors become quietly obsessed. It tastes nothing like the hotel breakfast version. You will learn to make tortillas by hand. Use freshly ground nixtamalized corn. Feel the dough shift from sticky to smooth. Pat it between your palms. Cook it on a comal until the edges brown. The kitchen fills with roasted-maize smell. This is the actual scent of rural Costa Rica. By the time the afternoon rain starts hammering the corrugated roof, you are sitting under cover eating what you made. The coffee comes from beans grown on the same property. The classes run regardless of weather. In September, this is the point.

Manuel Antonio is Costa Rica's most visited national park for good reason. September strips away the reason most experienced travelers avoid it: the crowds. The park opens at 7 AM. In September you can walk the main trail from the entrance to Playa Manuel Antonio with a naturalist guide and encounter white-faced capuchins dropping down to investigate you rather than performing for tour groups. The three-toed sloths in the cecropia trees along the beach trail are easier to spot when there are fewer people making noise below them. September mornings typically hold clear until noon or early afternoon. This gives you a solid window of warm, humid hiking under canopy where the air smells of damp leaf litter and the occasional sharp burst of wild ginger. The beaches inside the park are swimmable in the mornings when the Pacific is calmer. The warm water at roughly 27°C (81°F) makes the Caribbean feel comparatively tepid. The catch: afternoon storms roll in hard, and the park closes at 4 PM regardless. Plan your visit for first light. The squirrel monkeys (mono titi), endemic to this stretch of Pacific coast and classified as endangered, are most active in the early morning when they move through the secondary forest in troops of twenty to thirty, chattering and leaping between branches with a recklessness that seems impossible for an animal that small.