October in Mariehamn is the rainiest month of the year. In October, the weather in Mariehamn is typically cold. Average daily high temperature in October is about 9 degrees above zero. On average, Mariehamn has 12 rainy, 12 partly cloudy, 4 cloudy, and 3 sunny days in October. The rains are usually moderate. October as well as January, March, April, and November is considered the most uncomfortable time to visit Mariehamn.