If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Grand Marais: The hottest months are usually August and July, with an average temperature of 15°C, while the coldest months are January and February, with an average of -7°C. The snowiest months in Grand Marais are April, March, January and November, with each month seeing an average of 38 cm of snowfall.