Weather is probably a major factor when you plan your trip to Lac Sainte-Marie, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually July and August, with an average temperature of 18°C, while the coldest months are January and February, with an average of -7°C. The snowiest months in Lac Sainte-Marie are January, April, November and December, with each month seeing an average of 28 cm of snowfall.