August in Terceira Island is the sunniest and the warmest month of the year. In August, the weather in Terceira Island is typically warm. Average daily high temperature in August is about 23 degrees above zero. On average, Terceira Island has 15 sunny, 13 partly cloudy, and 3 rainy days in August. The rains are usually moderate. August as well as July is considered the most comfortable time to visit Terceira Island.