Weather will likely play an important role when you plan your trip to North Sioux City, 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 72°F, while the coldest months are January and February with an average of 27°F. The snowiest months in North Sioux City are January, October, February, and November, with each month seeing an average of 9 inches of snowfall.