The most popular time for Costa Rica vacations is the holiday peak season around Christmas and New Years but the best time to visit may be a couple of weeks later after the crowds thin.
The rains end in December but the forests remain lush into the new year while dry sunny weather prevails on the beaches. It’s one of the best times for wildlife when tropical species like monkeys and sloths are joined by migrant birds from the north, humpback whales giving birth in the warm waters, and sea turtles nesting on shore.
It's most commonly believed the best time to go to Costa Rica is between the months of December and April. In July and August, there’s a bit more rain but even fewer visitors and slightly lower prices and of course it’s great to travel during the secret dry season on the Caribbean in September and October.
In fact, there’s no bad time to go. It really depends on what your travel goals and priorities are.