Weather can make or break a road trip, so here's some data about year-round temperatures in Adel to help you plan yours: The hottest months are usually July and August, with an average temperature of 18°C, while the coldest months are December and January, with an average of -1°C. The snowiest months in Adel are January, March, February and April, with each month seeing an average of 24 cm of snowfall.