If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Sheridan: The hottest months are usually July and August, with an average temperature of 18°C, while the coldest months are February and December, with an average of -4°C. The snowiest months in Sheridan are February, January, October and April, with each month seeing an average of 18 cm of snowfall.