August in Aspen is the rainiest month of the year. In August, the weather in Aspen is typically warm. Average daily high temperature in August is about 21 degrees above zero. On average, Aspen has 14 rainy, 13 sunny, 3 partly cloudy, and 1 cloudy day in August. The rains are usually moderate. August as well as February, March, April, and May is considered the most uncomfortable time to visit Aspen.