Other facts from our historical weather data: Which is the warmest month in Yarm? July has an average maximum temperature of 20°C (68°F) and is the warmest month of the year. Which is the coldest month in Yarm? The coldest month is February with an average maximum temperature of 8°C (46°F). Which is the wettest month in Yarm? June tops the wettest month list with 74mm (2.9 in) of rainfall. Which is the driest month in Yarm? March is the driest month with 53mm (2.1 in) of precipitation. Which is the sunniest month in Yarm? May is the sunniest month with an average of 182 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.