If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Saint-Ouen: The hottest months are usually August and July with an average temp of 66°F, while the coldest months are January and February with an average of 42°F. The snowiest months in Saint-Ouen are February, March, January, and May, with each month seeing an average of 5 inches of snowfall.