Weather is probably a major factor when you plan your trip to Fort Simpson, and keep 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 temp of 59°F, while the coldest months are January and December with an average of -2°F. The snowiest months in Fort Simpson are January, February, December, and March, with each month seeing an average of 45 inches of snowfall.