Weather will likely play an important role when you plan your trip to Nampa, and keep 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 temp of 59°F, while the coldest months are February and December with an average of 12°F. The snowiest months in Nampa are January, October, February, and November, with each month seeing an average of 8 inches of snowfall.