March in Alpharetta is the rainiest month of the year. In March, the weather in Alpharetta is typically warm. Average daily high temperature in March is about 16 degrees above zero. On average, Alpharetta has 11 rainy, 11 sunny, 8 partly cloudy, and 1 cloudy day in March. The rains are usually heavy. March as well as January, February, July, and December is considered the most uncomfortable time to visit Alpharetta.