August in Cartagena is the cloudiest month of the year. In August, the weather in Cartagena is typically hot. Average daily high temperature in August is about 28 degrees above zero. On average, Cartagena has 22 rainy, 5 cloudy, and 4 partly cloudy days in August. The rains are usually heavy. August as well as May, June, July, and September is considered the most uncomfortable time to visit Cartagena.