Other facts from our historical weather data: Which is the warmest month in Cavan? 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 Cavan? The coldest month is January with an average maximum temperature of 9°C (48°F). Which is the wettest month in Cavan? August tops the wettest month list with 96mm (3.8 in) of rainfall. Which is the driest month in Cavan? March is the driest month with 73mm (2.9 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.