The whole country of Costa Rico is sometimes said to have a perfect climate, but let’s focus on the capital here. San Jose temperature statistics seem near perfect, with an average daily minimum temperature in the coldest months (December-January) of 14 C (57 F), and the hottest month (May) has an average daily maximum temperature of 26 C (79 F). It is, however, very wet for large parts of the year, with average monthly precipitation exceeding 200 mm (7.9 in) from May through to October.
See San Jose climate statistics at BBC.
Read more about San Jose at Answers.com.