Hello Jeremy, thankyou for your question.
Boise ,Idaho gets in the sub zero's but not drastically .
There is a listing of the "cold snaps" and other data concerning temperature at the first link below.
Note,this data starts in 1883 so you'll want to look through the years to get a reality of an overall view.
Here are Boises heaviest snowfalls (which can often help cold STAY cold!)
This link is a " just for fun",Thanksgiving day forecast which is looking very snowy tomorrow!
Would you please let me know if you need any more help?
Otherwise just click "Accept" and leave a positive feedback!