The Caribbean coast does its own thing weather-wise — when the rest of Costa Rica is in dry season, Puerto Viejo can be wet, and vice versa. The two best windows are September–October and February–April, which both tend to be drier and sunnier than the rest of the year.
December and January see big surf for Salsa Brava and lots of visitors; book ahead. May, June and November are the wettest months — heavy afternoon downpours, lush forests, and far fewer tourists. Turtle nesting runs from February to July; raptor migration is mid-October to mid-November. The temperature stays around 25–30°C all year.