Other facts from our historical weather data: Which is the warmest month in Garston? January has an average maximum temperature of 17°C (63°F) and is the warmest month of the year. Which is the coldest month in Garston? The coldest month is July with an average maximum temperature of 4°C (39°F). Which is the wettest month in Garston? December tops the wettest month list with 152mm (6 in) of rainfall. Which is the driest month in Garston? July is the driest month with 91mm (3.6 in) of precipitation. Which is the sunniest month in Garston? January is the sunniest month with an average of 230 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.