Because of Colombia's proximity to the equator, the country does not experience very extreme climate changes throughout the year. Instead the weather is constantly temperate with a dry season that last from December to March which is likewise the best time to travel to Colombia. It may also be a good idea to travel during August or September to take advantage of the lower prices of the off-season without getting hit with the hardest rains. The rainiest months are from May to July and from October to November.
Keep in mind that temperatures can vary dramatically based on the altitude, which ranges from sea level to 10,000 feet (3,050 meters). Coastal cities generally have year round daytime temperatures in the 70s to 80s (23°C to 32°C) that cool off to the 60s and 70s (17°C to 27°C) in the evenings. The inland daytime temperatures are generally like the evenings on the coast with temperatures in the 60s and 70s (17°C to 27°C) and evenings in the 40s or 50s (5°C to 16°C). Because of these cool temperatures, it is a good idea to have on hand a warm sweater for evenings on the coast and a jacket for the high altitude lows. The best time of year to visit the popular San Andrés archipelago is January, February, or September, while March and April are also gorgeous months.