Weather will likely play an important role when you plan your trip to Oslo, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually July and June, with an average temperature of 14°C, while the coldest months are January and February, with an average of -4°C. The snowiest months in Oslo are January, December, February and October, with each month seeing an average of 43 cm of snowfall.