August is the height of Costa Rica's "green" (rainy) season (May to November). During this month you can expect temperatures to be a few degrees cooler in most places, and also there will be more frequent rains. Know that if you're planning some beach time in places like Manuel Antonio National Park or other locales on the central and southern Pacific coast, there will likely be significant rainfall. That said, the northern Pacific Coast remains relatively dry even during this green season.
Crowds & Costs
The bright side of traveling during this low season is that in most parts of the country you'll find cheaper hotel prices and fewer crowds. Typical discounts are in the 15-20% range, but it's not uncommon to score hotel rooms for even 50% off during these low-season months. Of course, international flights will be cheaper as well. Fares offered by the main local carrier, Sansa Airlines, typically do not fluctuate all that much, but it's still possible to find discounts.
Where to Go
The prevailing wisdom regarding visits to Costa Rica during the green season is that you'll want to visit the areas with the least fluctuation in weather when compared to the dry season. Much of Guanacaste Province (especially the Nicoya Peninsula) enjoys a tropical dry climate year-round. Therefore the temperature fluctuation in many areas here is negligible, just a couple of degrees.
That means you can visit popular Pacific coastal destinations like Nosara, Tamarindo, Playa Guiones, and more while enjoying some decent weather but without the crowds and high-season prices. You should also consider visiting the Caribbean side of the country during August. The popular village of Puerto Viejo, located near the Panamanian border, enjoys its own mini-dry season during this time, so you'll find sunny beach weather here too.
If you come to Costa Rica at the beginning of August, and you plan on spending more than a day or two around the capital of San José, consider visiting the nearby city of Cartago. The Virgin of Los Angeles Day (Costa Rica's third-biggest religious festival after Christmas and Easter), takes place on August 2nd and is quite the sight to see (more on this below).
For more on where to go during the green season. read this article.
What to Do
Whitewater rafting is at its best during the rainy season, and whale watching is a fun activity best accessed from the remote Osa Peninsula. Surfing is also a good option on the sunny beaches of Puerto Viejo.
Each year some two million locals make the pilgrimage on foot from all corners of the country to the city of Cartago, which is the nation's colonial capital. Located here is the focus of the occasion, the Basilica de Nuestra Señora de Los Angeles (Our Lady of Los Angeles Church), the city's impressive baroque/gothic cathedral. Back in the 1600s supposedly a young local girl found a small black statue of the Virgin (La Negrita), which kept disappearing and reappearing in the same place—a sign that the locals were to build a cathedral in that particular spot.
If you do feel like taking part in this spiritual pilgrimage (known as the romería), be warned: it can be a multi-day affair depending on where you're coming from. Many come from San José, and even that 13-mile walk can take a couple days or longer. If you don't have the time to join the procession, feel free to visit Cartago on August 2nd and witness weary travelers making their way to the church (some even cross the threshold on their hands and knees in a show of humility and piety).
Events in August
Virgin of Los Angeles Day. On August 2nd every year scores of people make a pilgrimage to the cathedral at Cartago, where they pay their respects to the Virgin and ask for wishes to be granted.
San Ramon Patron Saint Day. August 30 marks the Festejos Patronoles, an annual festivity held in the town of San Ramon (outside San José), and features parades, live music, and dancing.
Traveling to Costa Rica in August? Check out these great itineraries.
Caribbean Coast Adventure. Spend a fun-filled week hiking in the rainforest, snorkeling in coral reefs, rafting the world-class rapids of Río Pacuare, and more. This itinerary is ideal for travelers heading to Costa Rica during the "green season" (May - November), as the Caribbean coast stays relatively dry during rainy months—and it's also the best time to see turtles nesting in Tortuguero National Park.
Costa Rica Whitewater and Surfing. From a whitewater rafting adventure along miles of tropical scenery on the Pacuare River to an excursion to one of the country's top surf spots, this short and sweet itinerary is jam-packed with thrilling aquatic experiences.