During the rainy season, humidity is higher and there is some inconvenience with the regular afternoon rains which are wonderously torrential but only last an hour or so. What to wear Panamanians are not charmed by grunge and you will be treated far better if your appearance is pleasant. However, during the dry season, there are days in the that hit the 90's. In the highlands, it gets cool at night and you will need a sweater or sweatshirt. During the rainy season, June through mid-December, there are afternoon torrential rains almost daily which usually last no more than an hour.
Humidity is high in Panama City and the lowlands during the rainy season.