August in Santiago de Compostela is the warmest month of the year. In August, the weather in Santiago de Compostela is typically warm. Average daily high temperature in August is about 21 degrees above zero. On average, Santiago de Compostela has 16 sunny, 11 partly cloudy, and 4 rainy days in August. The rains are usually light. August as well as July and September is considered the most comfortable time to visit Santiago de Compostela.