Why do people say it’s good to eat squash on the winter solstice in Japan?
If you are about to attain winter, then it's the winter solstice. Happy winter, everyone!
The reading for 冬 is the on'yomi reading, and one you haven't learned before. You're going to want to think about how you are celebrating the winter solstice in one particular place, that place being とうきょう (とう). See the Tokyo landmarks around you, think that you are there on the winter solstice, and also think about the things you are doing to celebrate, here in Tokyo. Also, watch out for the rendaku.