March in Siena is the windiest month of the year. In March, the weather in Siena is typically warm. Average daily high temperature in March is about 12 degrees above zero. On average, Siena has 13 rainy, 11 sunny, and 7 partly cloudy days in March. The rains are usually moderate. March as well as January, February, November, and December is considered the most uncomfortable time to visit Siena.