If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Butte: The hottest months are usually July and August, with an average temperature of 15°C, while the coldest months are December and January, with an average of -7°C. The snowiest months in Butte are February, April, October and March, with each month seeing an average of 20 cm of snowfall.