August in Viseu is the sunniest and the warmest month of the year. In August, the weather in Viseu is typically warm. Average daily high temperature in August is about 26 degrees above zero. On average, Viseu has 21 sunny, 5 partly cloudy, 4 rainy, and 1 cloudy day in August. The rains are usually light. August as well as July is considered the most comfortable time to visit Viseu.