Tamarindo, located in the Guanacaste province of Costa Rica, naturally has a tropical climate with an ongoing ocean breeze. Costa Rica is only nine degrees above the equator, so you can bet on warm weather all-year round. However, this usually means that there is a wet and dry season, the wet season being over the Northern Hemisphere's winter. Tamarindo however, is one of the driest areas in Costa Rica and is labeled as being a "tropical dry forest", the only one of this type in Central America. Therefore, what is the wet season for most of the Central America region, is called the "green season" in Tamarindo as it is green, but not wet. 

Here is a easy-to-read chart of what to expect.