Other facts from our historical weather data: When is summer in Colby?The hottest season / summer takes place in June, July, August and September. Does Colby have a dry season? Yes, the months of January, February, March and November are very dry. Which is the warmest month in Colby? July has an average maximum temperature of 33°C (91°F) and is the warmest month of the year. Which is the coldest month in Colby? The coldest month is January with an average maximum temperature of 6°C (43°F). Which is the wettest month in Colby? July tops the wettest month list with 92mm (3.6 in) of rainfall. Which is the driest month in Colby? January is the driest month with 6mm (0.2 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.