May in Alloa is the sunniest month of the year. In May, the weather in Alloa is typically warm. Average daily high temperature in May is about 12 degrees above zero. On average, Alloa has 17 rainy, 6 sunny, 6 cloudy, and 2 partly cloudy days in May. The rains are usually moderate. May as well as January, February, March, and April is considered the most uncomfortable time to visit Alloa.