Other facts from our historical weather data: Which months have the greatest rainfall in Mendocino? Most rainfall (rainy season) is seen in January, March and December. Does Mendocino have a dry season? Yes, the months of June, July, August and September are very dry. Which is the warmest month in Mendocino? 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 Mendocino? The coldest month is December with an average maximum temperature of 13°C (55°F). Which is the wettest month in Mendocino? December tops the wettest month list with 201mm (7.9 in) of rainfall. Which is the driest month in Mendocino? August is the driest month with 2mm (0.1 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.