Dark winter also does refer to a nuclear fallout
But I’d prefer the bunker option
Also winter starts on the winter solstice (longest night of year compared to summer solstice which is longest day) December 21 or 22 usually.. this year it’s 21
It starts 12 days of Yuletide .. also the 3 shortest days/longest night where the sun will begin it’s ascension back into the sky and days start to get longer again. They considered the sun disappearing to the underworld on those 3 days where it didn’t move from its celestial path.
The 3 days also referred to the 3 days that Jesus was in underworld.. or Osiris as well.. 22,23,24 on the 25th the ‘Sun’ rose from the underworld and ascended back into the heavens bringing light and warmth once again
Very symbolic and beautiful stories for how we perceived the world.. not always literal but figurative or metaphorical/parabolic