Other facts from our historical weather data: When is the rainy season in Stumm? Rainy season in Stumm occurs in the months of May, June, July and August. When is winter in Stumm? The coldest season / winter is in the following months: January, February and December. Which is the warmest month in Stumm? August has an average maximum temperature of 19°C (66°F) and is the warmest month of the year. Which is the coldest month in Stumm? The coldest month is January with an average maximum temperature of -1°C (30°F). Which is the wettest month in Stumm? June tops the wettest month list with 208mm (8.2 in) of rainfall. Which is the driest month in Stumm? January is the driest month with 90mm (3.5 in) of precipitation. Which is the sunniest month in Stumm? May is the sunniest month with an average of 185 hours of sunshine. No idea where to travel to this year? We have a tool that recommends destinations based on your ideal conditions. Find out where to go with our weather planner.