Panama has a tropical climate. Temperatures are relatively high and vary little throughout the year. The temperatures are usually lower on the Pacific than on the Caribbean coast.
The best thing about the weather in Panama City is that it is always warm through the year. You will enjoy daily highs of up to 24° C (75.2° F) to 35° C (95° F) with nights being velvet warm at 20° C (68° F) to 24° C (72.2 F) degrees. Those looking for cooler climate can find it in the Highlands of Panama in Chiriquí, Cerro Punta and the Anton Valley with daily high at 22° C (71-6° F) and cool fresh nights at to 24° C (72.2° F). Panama has two seasons the dry season from December to end of April, and the wet season, from May until November.
38TH IAHR World Congress will be held during September which means that you will experience the middle of the rainy season -Temperature will remains the same with a variety on the humidity that increase during rainy days, rains normally happen early in the morning, or in the afternoon but for a long period so the rest of the day you will enjoy a sunny tropical weather.