Other facts from our historical weather data: When is summer in Grants Pass?The hottest season / summer takes place in June, July, August and September. Does Grants Pass have a dry season? Yes, the months of July, August and September are very dry. Which is the warmest month in Grants Pass? July has an average maximum temperature of 32°C (90°F) and is the warmest month of the year. Which is the coldest month in Grants Pass? The coldest month is December with an average maximum temperature of 8°C (46°F). Which is the wettest month in Grants Pass? December tops the wettest month list with 166mm (6.5 in) of rainfall. Which is the driest month in Grants Pass? August is the driest month with 5mm (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.