Other facts from our historical weather data: Does Three Rivers have a dry season? Yes, the months of May, June, July, August and September are very dry. Which is the warmest month in Three Rivers? July has an average maximum temperature of 37°C (99°F) and is the warmest month of the year. Which is the coldest month in Three Rivers? The coldest month is December with an average maximum temperature of 14°C (57°F). Which is the wettest month in Three Rivers? December tops the wettest month list with 106mm (4.2 in) of rainfall. Which is the driest month in Three Rivers? August is the driest month with 0mm (0 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.