Other facts from our historical weather data: Which is the warmest month in Granheim? July has an average maximum temperature of 18°C (64°F) and is the warmest month of the year. Which is the coldest month in Granheim? The coldest month is December with an average maximum temperature of -3°C (27°F). Which is the wettest month in Granheim? July tops the wettest month list with 106mm (4.2 in) of rainfall. Which is the driest month in Granheim? February is the driest month with 51mm (2 in) of precipitation. 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.