Other facts from our historical weather data: Which months have the greatest rainfall in Diamond Rock? Most rainfall (rainy season) is seen in October, November and December. Which is the hottest month in Diamond Rock? September has an average maximum temperature of 30°C (86°F) and is the hottest month of the year. Which is the coolest month in Diamond Rock? The coolest month is January with an average maximum temperature of 27°C (81°F). Which is the wettest month in Diamond Rock? October tops the wettest month list with 280mm (11 in) of rainfall. Which is the driest month in Diamond Rock? April is the driest month with 27mm (1.1 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.