From the 6 years I spent in the States, don't remember a time when the border was closed - unless there are extenuating circumstances. Quite to the contrary, I would think that CBSA and DHS would post more officers due to increased traffice over the holidays. Just my logic!
You can always check border wait times at the following link:
www . cbsa-asfc.gc.ca/bwt-taf/menu-eng . html