Other facts from our historical weather data: Does Williams have a dry season? Yes, the months of May, June, July, August and September are very dry. Which is the warmest month in Williams? July has an average maximum temperature of 35°C (95°F) and is the warmest month of the year. Which is the coldest month in Williams? The coldest month is December with an average maximum temperature of 13°C (55°F). Which is the wettest month in Williams? December tops the wettest month list with 76mm (3 in) of rainfall. Which is the driest month in Williams? 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.