May in Fort Augustus is the sunniest month of the year. In May, the weather in Fort Augustus is typically cold. Average daily high temperature in May is about 10 degrees above zero. On average, Fort Augustus has 25 rainy, 3 sunny, 2 cloudy, and 1 partly cloudy day in May. The rains are usually moderate. May as well as January, February, March, and April is considered the most uncomfortable time to visit Fort Augustus.