Weather will likely play an important role when you plan your trip to Saint John, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and July, with an average temperature of 18°C, while the coldest months are February and January, with an average of -11°C. The snowiest months in Saint John are April, March, October and January, with each month seeing an average of 33 cm of snowfall.