Weather will likely play an important role when you plan your trip to Challis, 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 17°C, while the coldest months are January and December, with an average of -6°C. The snowiest months in Challis are February, January, December and March, with each month seeing an average of 14 cm of snowfall.