If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Oskaloosa: 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 29°F. The snowiest months in Oskaloosa are January, November, December, and February, with each month seeing an average of 7 inches of snowfall.