This is an incomplete list of festivals and holidays that take place during the winter in the northern hemisphere, especially those commemorating the season. Many festivals of light take place in this period since the shortest day of the year in the northern hemisphere is the Winter Solstice.
Holidays are listed in chronological order under each heading.
Bodhi Day: December 8 - Day of Enlightenment, celebrating the day that the historical Buddha (Shakyamuni or Siddhartha Guatama) experienced enlightenment (also known as Bodhi).
Celtic
Samhain: November 1 - first day of winter in the Celtic calendar (and Celtic New Year's Day)
Navratri:Nine-day celebration worshipping female divinity, in October or November. Culminates in Dussehra.
Diwali:Known as the Festival of Lights, this Hindu holiday celebrates the victory of good over evil. The five-day festival is marked by ceremonies, fireworks and sweets. Women dress up and decorate their hands with henna tattoos for the melas, or fairs. Many different myths are associated with Diwali, one of which celebrates the return of Lord Rama after a 14-year exile and his defeat of the demon Ravana.
Hanukkah: Starting on 25 Kislev (Hebrew) or various dates in November or December (Gregorian) - eight day festival commemorating the miracle of the oil after the desecration of the Temple by Antiochus IV Epiphanes and his defeat in 165 BCE.
Tu Bishvat: New Year of the Trees occurring on the 15th of Shevat, January or February.
Purim: Occurring on 14th or 15th day of Adar, late February to March, commemorating the miraculous deliverance and victory of the Jews of the Persian Empire in the events recorded in the Book of Esther
Muslim
Eid ul-Adha: Starting on the 10th of Dhul Hijja, a four day holiday commemorating the Prophet Ibrahim's willingness to sacrifice his son, Ishmael.
NOTE: The Islamic calendar is based on the moon and this festival moves with respect to the solar year. It is, however, falling in the winter in the first decade of the present [21st] Century of the common era.
Pagan and Neo-Pagan
Samhain: November 1 - first day of winter in the Celtic calendar (and Celtic New Year's Day)
Yule: (Winter Solstice) - Germanic and Egyptian Pagan festival of the rebirth of the Sun
Holiday: This Pastafarian holiday starts around the beginning of winter and lasts till around the end of winter, and is intentionally vague, that one can develop his/her own family tradition (although some involvement by beer and pasta are preferred).
Persian
Sadeh: A mid-winter feast to honor fire and to "defeat the forces of darkness, frost and cold".
Yalda: The turning point, Winter Solstice (December 21). End of the longest night of the year (Darkness), and beginning of growing of the days (Lights). A celebration of Good over Evil.
Chahar Shanbeh Suri: Festival of Fire, Last Wednesday of the Iranian Calendar year. It marks the importance of the light over the darkness, and arrival of spring and revival of nature.
Polynesian
Matariki: (M?ori New Year, usually early June) - Rising of the Pleiades star cluster before dawn.
Winterval: Secular name for winter festivities coined by Birmingham City Council to encompass all holidays being recognized from October to January
Sydney Winter Festival: Winter Festival recreates the magic of traditional European winter celebrations, including a variety of culinary delights, and first class entertainment on an expansive outdoor screen. From August 1-10th 2008
Chrismukkah: the modern-day merging of the holidays of Christianity's Christmas and Judaism's Hanukkah.
Chrismahanukwanzakah: the modern-day merging of the holidays of Christianity's Christmas, Judaism's Hanukkah, and the African-American holiday of Kwanzaa.
Hedgehog Day: February 2 - supposed archaic European version of Groundhog Day, dating back to Roman times.
Wintersday: The annual winter holiday in the MMORPG Guild Wars. This holiday is based on Christmas and Yule and one can get neat hats.
Starlight Celebration: The annual winter holiday based on Christmas/Yule/winter solstice in the MMORPG Final Fantasy XI (aka FFXI). Players can collect various holiday equipment, Mog house furnishings, fireworks, and food.
Couch burning June 21 Southern Winter solstice. A couch is burnt on a bonfire on the 21st of June, inspired by the Burning Man festival and conducted by CouchSurfers.