Other facts from our historical weather data: Which is the warmest month in Newton Stewart? August has an average maximum temperature of 18°C (64°F) and is the warmest month of the year. Which is the coldest month in Newton Stewart? The coldest month is February with an average maximum temperature of 8°C (46°F). Which is the wettest month in Newton Stewart? October tops the wettest month list with 146mm (5.7 in) of rainfall. Which is the driest month in Newton Stewart? May is the driest month with 85mm (3.3 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.