August in Tromsø is the rainiest month of the year. In August, the weather in Tromsø is typically warm. Average daily high temperature in August is about 12 degrees above zero. On average, Tromsø has 24 rainy, 4 sunny, 2 cloudy, and 1 partly cloudy day in August. The rains are usually heavy. August as well as April, May, June, and July is considered the most uncomfortable time to visit Tromsø.