If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Boise: The hottest months are usually July and August, with an average temperature of 22°C, while the coldest months are January and December, with an average of 0°C. The snowiest months in Boise are January, March, December and February, with each month seeing an average of 23 cm of snowfall.