May in Altoona is the rainiest month of the year. In May, the weather in Altoona is typically warm. Average daily high temperature in May is about 19 degrees above zero. On average, Altoona has 17 rainy, 7 sunny, 4 partly cloudy, and 3 cloudy days in May. The rains are usually heavy. May as well as February, March, April, and December is considered the most uncomfortable time to visit Altoona.