Other facts from our historical weather data: Which is the warmest month in Arnside? July has an average maximum temperature of 19°C (66°F) and is the warmest month of the year. Which is the coldest month in Arnside? The coldest month is February with an average maximum temperature of 7°C (45°F). Which is the wettest month in Arnside? December tops the wettest month list with 159mm (6.3 in) of rainfall. Which is the driest month in Arnside? April is the driest month with 87mm (3.4 in) of precipitation. Which is the sunniest month in Arnside? May is the sunniest month with an average of 217 hours of sunshine. 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.