Other facts from our historical weather data: Which is the warmest month in Cairnryan? August has an average maximum temperature of 17°C (63°F) and is the warmest month of the year. Which is the coldest month in Cairnryan? The coldest month is February with an average maximum temperature of 9°C (48°F). Which is the wettest month in Cairnryan? October tops the wettest month list with 146mm (5.7 in) of rainfall. Which is the driest month in Cairnryan? May is the driest month with 75mm (3 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.