Small country in terms of area, there is a lot of things in terms of weather in Costa Rica. Diverse and variable weather, Costa Rica can be categorized into few climatic zones, each of which are distinct and individual. Though generally classified as a tropical country because of its close proximity to the equator, Costa Rica has no real winter period, and the sun shines here throughout the year. With 12 hours of sunshine a day, the sun rises about 5 h and sets at about 18 h.
Principal reason for the diversity in the weather in Costa Rica is the elevations at different parts of the country. Guanacaste has a dry climate through the whole year, while Monteverde is misty and foggy through the year due to its elevation, a higher elevation. San Jose, Central Valley, has the best climate in the country as the weather here is on one average of 72 degrees Fahrenheit or 22 degrees Celsius.
The average annual temperature is around 70-81 degrees Fahrenheit or 21-27 degrees Celsius and coolest months of the year are from November to middle February. From March to May is when the weather has his humid time with rains all over the country.
There is no real winter or even summer(more defined as the winter) in Costa Rica, and the rainy season from April to October, with the months of November through May having little to no rain and August to September being the heaviest rain period in the country. It's also important to keep in mind that Caribbean coast is rather unique than other zones and has its own microclimate throughout the year.