Other facts from our historical weather data: Which is the warmest month in Sletta? August has an average maximum temperature of 16°C (61°F) and is the warmest month of the year. Which is the coldest month in Sletta? The coldest month is February with an average maximum temperature of 4°C (39°F). Which is the wettest month in Sletta? December tops the wettest month list with 186mm (7.3 in) of rainfall. Which is the driest month in Sletta? May is the driest month with 89mm (3.5 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.