Other facts from our historical weather data: Which is the warmest month in Capel Celyn? July has an average maximum temperature of 19°C (66°F) and is the warmest month of the year. Which is the coldest month in Capel Celyn? The coldest month is February with an average maximum temperature of 7°C (45°F). Which is the wettest month in Capel Celyn? December tops the wettest month list with 131mm (5.2 in) of rainfall. Which is the driest month in Capel Celyn? April is the driest month with 91mm (3.6 in) of precipitation. Which is the sunniest month in Capel Celyn? May is the sunniest month with an average of 169 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.