Other facts from our historical weather data: Which is the warmest month in Lannion? August has an average maximum temperature of 20°C (68°F) and is the warmest month of the year. Which is the coldest month in Lannion? The coldest month is February with an average maximum temperature of 11°C (52°F). Which is the wettest month in Lannion? December tops the wettest month list with 128mm (5 in) of rainfall. Which is the driest month in Lannion? July is the driest month with 49mm (1.9 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.