The weather in Costa Rica in unfathomable, Truly! Difficult to predict, impossible to know. It is the tropics, and the tropics are unpredictable. However, we will give it a try, by dividing the country into four areas:

North and Central Pacific Coast (Where Puntarenas is):

Sunny Season: Early November to late May.

January can be very windy in Monteverde, Miravalles and Rincon de la Vieja.

North Pacific Coast: Guanacaste

North Pacific Mountains: Rincón de la Vieja, Monteverde.

Central Pacific Area: Jacó, Manuel Antonio, and Dominical

Central Area:

Sunny Season: Late December (Around the 20^th.) to the end of May (Around the 20^th ).

December and January are usually chillier and windy. (Temperature comes down a couple of degrees in these two months). There are two short periods (Or two weeks each) in late June and early November when it is sunny.

Central Valley: San José, Alajuela, Heredia, Cartago and San Ramón.

Talamanca Mountain Range: Zona de los Santos (San Gerardo de Dota).

South Pacific Area:

Sunny Season: December to June.

South Pacific Area: Osa Peninsula, Golfo Dulce.

North Area and Caribbean Coast Area:

Sunny Season:
Late February, March, and April. September and October.

North Caribbean: Tortuguero.

South Caribbean: Cahuita, Puerto Viejo, Manzanillo, and Bocas del Toro (Panama). This may include Turrialba Volcano area.

North Area: Sarapiquí and Arenal Volcano and some areas in the Central Volcanic Mountain Range (Poas Volcano, Waterfall Gardens).

This calendar may seem a bit complicated, but it is important to realize that in the tropics there are no weather fixed rules. January and February can be influenced by North cold fronts (And now and then even March). September and October by hurricanes, and December by the trade winds… Always recommend rain gear! No matter what!