Other facts from our historical weather data: Which is the warmest month in St Helens? February has an average maximum temperature of 20°C (68°F) and is the warmest month of the year. Which is the coldest month in St Helens? The coldest month is August with an average maximum temperature of 13°C (55°F). Which is the wettest month in St Helens? November tops the wettest month list with 77mm (3 in) of rainfall. Which is the driest month in St Helens? May is the driest month with 42mm (1.7 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.