17-19 Feb this winter. Well worth a visit. The Snow Carnival at night is cool with some amazing fireworks afterwards and loads of other things going on around the town.
I recommend the Ouchijuku Snow Festival held every February in Fukushima. For one weekend every year the historic post town of Ouchi, a village of thatched roof homes, hosts yosakoi dancing, traditional arts, a fireworks display, and sampling of local specialties. Snow lanterns line the main street. The view is breathtaking.
Stay overnight in nearby Ashinomaki Onsen or Yunokami Onsen.
*In 2017, the festival will be held on Saturday, Feb. 11 and Sunday, Feb. 12.