The coldest one around here was in, hmm, winter of 2003-2004, or 2004-2005; one very deep snow, and then no thaw until March because of the cold temperatures. Another very cold one was 1998-1999 if memory serves; a restaurant that I used to frequent had a small parking lot, and the plowed snow pile didn’t finally vanish until nearly June (once the trees leafed out it was in the shade, but still...).
However, the worst storm I ever saw:
https://search.brave.com/search?q=winter+storm+of+1978
My folks were in the 78 blizzard
Lost power and had to huddle by the fire in blankets.
They were on a list of evacuees, but the power did return.
I was on the West coast and couldn’t reach them for hours.
The 1978 storm has been mentioned here by quite a few. I remember us getting really heavy snow in Wisconsin - I think it was New Year’s Eve and all of us dopey teens were out in it!