Other facts from our historical weather data: Which is the warmest month in Greencastle? 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 Greencastle? The coldest month is February with an average maximum temperature of 9°C (48°F). Which is the wettest month in Greencastle? November tops the wettest month list with 148mm (5.8 in) of rainfall. Which is the driest month in Greencastle? May is the driest month with 86mm (3.4 in) of precipitation. Which is the sunniest month in Greencastle? May is the sunniest month with an average of 203 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.