Other facts from our historical weather data: When is summer in Chillicothe?The hottest season / summer takes place in June, July, August and September. Which is the warmest month in Chillicothe? July has an average maximum temperature of 31°C (88°F) and is the warmest month of the year. Which is the coldest month in Chillicothe? The coldest month is January with an average maximum temperature of 3°C (37°F). Which is the wettest month in Chillicothe? August tops the wettest month list with 137mm (5.4 in) of rainfall. Which is the driest month in Chillicothe? January is the driest month with 23mm (0.9 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.