Other facts from our historical weather data: Which months have the greatest rainfall in Grossarl? Most rainfall (rainy season) is seen in May, June, July and August. When is winter in Grossarl? The coldest season / winter is in the following months: January, February and December. Which is the warmest month in Grossarl? 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 Grossarl? The coldest month is January with an average maximum temperature of -2°C (28°F). Which is the wettest month in Grossarl? June tops the wettest month list with 179mm (7 in) of rainfall. Which is the driest month in Grossarl? January is the driest month with 87mm (3.4 in) of precipitation. Which is the sunniest month in Grossarl? July is the sunniest month with an average of 178 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.