If you're looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Dickinson: The hottest months are usually July and August, with an average temperature of 20°C, while the coldest months are February and January, with an average of -6°C. The snowiest months in Dickinson are October, February, April and December, with each month seeing an average of 13 cm of snowfall.