When to Go
High Season: Mid-December to April
Climate is difficult to pinpoint in this vast region. The Northern Lowlands link the rainier Caribbean in the east to drier Guanacaste in the west. Precipitation generally decreases from east to west. Monteverde is cool, damp, and breezy much of the time, with high winds in January and February. Elsewhere, rain can occur outside the official wet season since the area's low elevation frequently hosts battles between competing weather fronts. Visibility changes daily (and hourly), so your chances of seeing the Arenal volcano crater is more or less the same year-round, though you may have more luck from February to April, the hottest and driest time of the year.
Low Season: June to mid-November
Throughout the entire region, the warm and humid rainy season normally lasts from June to December. Many places in Arenal and Monteverde are beginning to impose high-season rates in July and August to correspond with prime North American and European vacation times.
We frequently overhear comments such as "I didn't know it would be so rainy in the rain forest." You heard it here first: that's why they call it the rain forest! During the rainy season it's not unusual for it to rain for several days straight, and even during the dry season, brief showers will come up without notice. Be sure to bring a poncho or rain jacket and waterproof footwear.
Shoulder Season: May through June
The wet season just starts to kick in by May, but rarely to a degree that will interfere with your travels. A little precipitation provides a welcome clearing and freshness of the air in the countryside.