Other facts from our historical weather data: When is summer in Sterling?The hottest season / summer takes place in June, July, August and September. Does Sterling have a dry season? Yes, the months of January, February, March, November and December are very dry. Which is the warmest month in Sterling? 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 Sterling? The coldest month is December with an average maximum temperature of 5°C (41°F). Which is the wettest month in Sterling? July tops the wettest month list with 78mm (3.1 in) of rainfall. Which is the driest month in Sterling? 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.