August in Milford Sound is the cloudiest month of the year. In August, the weather in Milford Sound is typically cold. Average daily high temperature in August is about 9 degrees above zero. On average, Milford Sound has 18 rainy, 8 partly cloudy, 4 sunny, and 1 cloudy day in August. The rains are usually heavy. August as well as January, February, March, and April is considered the most uncomfortable time to visit Milford Sound.