Other facts from our historical weather data: Which is the warmest month in Newhaven? August has an average maximum temperature of 20°C (68°F) and is the warmest month of the year. Which is the coldest month in Newhaven? The coldest month is February with an average maximum temperature of 9°C (48°F). Which is the wettest month in Newhaven? November tops the wettest month list with 123mm (4.8 in) of rainfall. Which is the driest month in Newhaven? May is the driest month with 53mm (2.1 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.