Panama lies in the tropics just north of the Equator, so temperatures are fairly constant all year round, just varying with altitude. At sea level, temperatures are a tropical 30-35°C, tempered by sea breezes. Up in the highlands temperatures generally hover around 15-19°C. Humidity tends to be high throughout the country and in terms of rainfall, the Caribbean side of the country tends to receive more rainfall than the Pacific side.
December to April denotes Panama's dry season and is generally the favoured time of year for visitors but usually only Christmas and the week before Easter are very busy. Places on the Caribbean side of the country, such as Bocas del Toro have a shorter dry season, but it is not uncommon for Bocas del Toro to receive at least one torrential downpour on a weekly basis throughout the year.
May to November is the rainy season with travel being less popular over this time. However the scenery is greener, the prices can be lower and if you are planning to dive or snorkel the water visibility is better. September is generally the wettest month in Panama City.
Panama is outside of the hurricane belt.